Merge branch 'master' into update_default_hsts_max_age

659 files changed, 7493 insertions, 6371 deletions

diff --git a/.codeclimate.yml b/.codeclimate.yml
index d59a0780d1..e4568d9d8b 100644
--- a/.codeclimate.yml
+++ b/.codeclimate.yml
@@ -23,7 +23,7 @@ checks:
 engines:
   rubocop:
     enabled: true
-    channel: rubocop-0-51
+    channel: rubocop-0-52
 
 ratings:
   paths:
diff --git a/.gitignore b/.gitignore
index da3b42cfbb..ab9ca8a6ac 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,25 +1,16 @@
-# Don't put *.swp, *.bak, etc here; those belong in a global ~/.gitignore.
+# Don't put *.swp, *.bak, etc here; those belong in a global .gitignore.
 # Check out https://help.github.com/articles/ignoring-files for how to set that up.
 
 .Gemfile
-.ruby-version
 .byebug_history
-debug.log
-pkg
+.ruby-version
+/*/doc/
+/*/test/tmp/
 /.bundle
-/dist
-/doc/rdoc
-/*/doc
-/*/test/tmp
-/activerecord/sqlnet.log
-/activemodel/test/fixtures/fixture_database.sqlite3
-/activesupport/test/fixtures/isolation_test
-/activestorage/test/service/configurations.yml
-/railties/test/500.html
-/railties/test/fixtures/tmp
-/railties/test/initializer/root/log
-/railties/doc
-/railties/tmp
-/guides/output
+/dist/
+/doc/
+/guides/output/
+debug.log
 node_modules/
-/actionview/log
+package-lock.json
+pkg/
diff --git a/.rubocop.yml b/.rubocop.yml
index a04de4b497..3c765d5b1d 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,5 +1,5 @@
 AllCops:
-  TargetRubyVersion: 2.2
+  TargetRubyVersion: 2.4
   # RuboCop has a bunch of cops enabled by default. This setting tells RuboCop
   # to ignore them, so only the ones explicitly set in this file are enabled.
   DisabledByDefault: true
@@ -26,6 +26,9 @@ Layout/CaseIndentation:
 Layout/CommentIndentation:
   Enabled: true
 
+Layout/ElseAlignment:
+  Enabled: true
+
 Layout/EmptyLineAfterMagicComment:
   Enabled: true
 
@@ -140,6 +143,7 @@ Style/UnneededPercentQ:
 Lint/EndAlignment:
   Enabled: true
   EnforcedStyleAlignWith: variable
+  AutoCorrect: true
 
 # Use my_method(my_arg) not my_method( my_arg ) or my_method my_arg.
 Lint/RequireParentheses:
@@ -152,3 +156,7 @@ Style/RedundantReturn:
 Style/Semicolon:
   Enabled: true
   AllowAsExpressionSeparator: true
+
+# Prefer Foo.method over Foo::method
+Style/ColonMethodCall:
+  Enabled: true
diff --git a/.travis.yml b/.travis.yml
index 1f18478919..2513e87114 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,8 @@ language: ruby
 sudo: false
 
 cache:
-  bundler: true
   directories:
+    - vendor/bundle
     - /tmp/cache/unicode_conformance
     - /tmp/beanstalkd-1.10
     - node_modules
@@ -60,9 +60,7 @@ env:
     - "GEM=ac:integration"
 
 rvm:
-  - 2.2.8
-  - 2.3.5
-  - 2.4.2
+  - 2.4.3
   - 2.5.0
   - ruby-head
 
@@ -70,19 +68,7 @@ matrix:
   include:
     - rvm: 2.5.0
       env: "GEM=av:ujs"
-    - rvm: 2.2.8
-      env: "GEM=aj:integration"
-      services:
-        - memcached
-        - redis-server
-        - rabbitmq
-    - rvm: 2.3.5
-      env: "GEM=aj:integration"
-      services:
-        - memcached
-        - redis-server
-        - rabbitmq
-    - rvm: 2.4.2
+    - rvm: 2.4.3
       env: "GEM=aj:integration"
       services:
         - memcached
@@ -100,30 +86,30 @@ matrix:
         - memcached
         - redis-server
         - rabbitmq
-    - rvm: 2.3.5
+    - rvm: 2.5.0
       env:
         - "GEM=ar:mysql2 MYSQL=mariadb"
       addons:
         mariadb: 10.2
-    - rvm: 2.3.5
+    - rvm: 2.5.0
       env:
         - "GEM=ar:sqlite3_mem"
-    - rvm: 2.3.5
+    - rvm: 2.5.0
       env:
         - "GEM=ar:postgresql POSTGRES=9.2"
       addons:
         postgresql: "9.2"
-    - rvm: jruby-9.1.15.0
+    - rvm: jruby-head
       jdk: oraclejdk8
       env:
         - "GEM=ap"
-    - rvm: jruby-9.1.15.0
+    - rvm: jruby-head
       jdk: oraclejdk8
       env:
         - "GEM=am,amo,aj"
   allow_failures:
     - rvm: ruby-head
-    - rvm: jruby-9.1.15.0
+    - rvm: jruby-head
     - env: "GEM=ac:integration"
   fast_finish: true
 
diff --git a/Gemfile b/Gemfile
index 1bc9863cc4..aada2bde1e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -38,11 +38,8 @@ gem "rubocop", ">= 0.47", require: false
 # https://github.com/guard/rb-inotify/pull/79
 gem "rb-inotify", github: "matthewd/rb-inotify", branch: "close-handling", require: false
 
-# https://github.com/puma/puma/pull/1345
-gem "stopgap_13632", platforms: :mri if RUBY_VERSION == "2.2.8"
-
 group :doc do
-  gem "sdoc", github: "robin850/sdoc", branch: "upgrade"
+  gem "sdoc", "~> 1.0"
   gem "redcarpet", "~> 3.2.3", platforms: :ruby
   gem "w3c_validators"
   gem "kindlerb", "~> 1.2.0"
@@ -52,6 +49,7 @@ end
 gem "dalli", ">= 2.2.1"
 gem "listen", ">= 3.0.5", "< 3.2", require: false
 gem "libxml-ruby", platforms: :ruby
+gem "connection_pool", require: false
 
 # for railties app_generator_test
 gem "bootsnap", ">= 1.1.0", require: false
@@ -130,7 +128,7 @@ platforms :ruby, :mswin, :mswin64, :mingw, :x64_mingw do
 
   group :db do
     gem "pg", ">= 0.18.0"
-    gem "mysql2", ">= 0.4.4"
+    gem "mysql2", ">= 0.4.10"
   end
 end
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 8c9b1c7388..baac1cee7e 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -23,74 +23,66 @@ GIT
     queue_classic (3.2.0.RC1)
       pg (>= 0.17, < 2.0)
 
-GIT
-  remote: https://github.com/robin850/sdoc.git
-  revision: 0e340352f3ab2f196c8a8743f83c2ee286e4f71c
-  branch: upgrade
-  specs:
-    sdoc (1.0.0.rc2)
-      rdoc (~> 5.0)
-
 PATH
   remote: .
   specs:
-    actioncable (5.2.0.beta2)
-      actionpack (= 5.2.0.beta2)
+    actioncable (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
       nio4r (~> 2.0)
-      websocket-driver (~> 0.6.1)
-    actionmailer (5.2.0.beta2)
-      actionpack (= 5.2.0.beta2)
-      actionview (= 5.2.0.beta2)
-      activejob (= 5.2.0.beta2)
+      websocket-driver (>= 0.6.1)
+    actionmailer (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      actionview (= 6.0.0.alpha)
+      activejob (= 6.0.0.alpha)
       mail (~> 2.5, >= 2.5.4)
       rails-dom-testing (~> 2.0)
-    actionpack (5.2.0.beta2)
-      actionview (= 5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
+    actionpack (6.0.0.alpha)
+      actionview (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       rack (~> 2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actionview (5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
+    actionview (6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activejob (5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
+    activejob (6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       globalid (>= 0.3.6)
-    activemodel (5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
-    activerecord (5.2.0.beta2)
-      activemodel (= 5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
+    activemodel (6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
+    activerecord (6.0.0.alpha)
+      activemodel (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       arel (>= 9.0)
-    activestorage (5.2.0.beta2)
-      actionpack (= 5.2.0.beta2)
-      activerecord (= 5.2.0.beta2)
+    activestorage (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      activerecord (= 6.0.0.alpha)
       marcel (~> 0.3.1)
-    activesupport (5.2.0.beta2)
+    activesupport (6.0.0.alpha)
       concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (~> 0.7)
+      i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-    rails (5.2.0.beta2)
-      actioncable (= 5.2.0.beta2)
-      actionmailer (= 5.2.0.beta2)
-      actionpack (= 5.2.0.beta2)
-      actionview (= 5.2.0.beta2)
-      activejob (= 5.2.0.beta2)
-      activemodel (= 5.2.0.beta2)
-      activerecord (= 5.2.0.beta2)
-      activestorage (= 5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
+    rails (6.0.0.alpha)
+      actioncable (= 6.0.0.alpha)
+      actionmailer (= 6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      actionview (= 6.0.0.alpha)
+      activejob (= 6.0.0.alpha)
+      activemodel (= 6.0.0.alpha)
+      activerecord (= 6.0.0.alpha)
+      activestorage (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       bundler (>= 1.3.0)
-      railties (= 5.2.0.beta2)
+      railties (= 6.0.0.alpha)
       sprockets-rails (>= 2.0.0)
-    railties (5.2.0.beta2)
-      actionpack (= 5.2.0.beta2)
-      activesupport (= 5.2.0.beta2)
+    railties (6.0.0.alpha)
+      actionpack (= 6.0.0.alpha)
+      activesupport (= 6.0.0.alpha)
       method_source
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
@@ -115,7 +107,7 @@ GEM
     archive-zip (0.7.0)
       io-like (~> 0.3.0)
     arel (9.0.0)
-    ast (2.3.0)
+    ast (2.4.0)
     aws-partitions (1.20.0)
     aws-sdk-core (3.3.0)
       aws-partitions (~> 1.0)
@@ -216,7 +208,7 @@ GEM
       em-socksify (>= 0.3)
       eventmachine (>= 1.0.3)
       http_parser.rb (>= 0.6.0)
-    em-socksify (0.3.1)
+    em-socksify (0.3.2)
       eventmachine (>= 1.0.0.beta.4)
     erubi (1.7.0)
     et-orbi (1.0.8)
@@ -274,7 +266,7 @@ GEM
     hiredis (0.6.1-java)
     http_parser.rb (0.6.0)
     httpclient (2.8.3)
-    i18n (0.9.1)
+    i18n (1.0.0)
       concurrent-ruby (~> 1.0)
     io-like (0.3.0)
     jdbc-mysql (5.1.44)
@@ -313,11 +305,11 @@ GEM
     mini_magick (4.8.0)
     mini_mime (0.1.4)
     mini_portile2 (2.3.0)
-    minitest (5.11.1)
+    minitest (5.11.3)
     minitest-bisect (1.4.0)
       minitest-server (~> 1.0)
       path_expander (~> 1.0)
-    minitest-server (1.0.4)
+    minitest-server (1.0.5)
       minitest (~> 5.0)
     mocha (1.3.0)
       metaclass (~> 0.0.1)
@@ -329,12 +321,12 @@ GEM
     multi_json (1.12.2)
     multipart-post (2.0.0)
     mustache (1.0.5)
-    mustermann (1.0.0)
-    mysql2 (0.4.9)
-    mysql2 (0.4.9-x64-mingw32)
-    mysql2 (0.4.9-x86-mingw32)
-    nio4r (2.1.0)
-    nio4r (2.1.0-java)
+    mustermann (1.0.2)
+    mysql2 (0.4.10)
+    mysql2 (0.4.10-x64-mingw32)
+    mysql2 (0.4.10-x86-mingw32)
+    nio4r (2.2.0)
+    nio4r (2.2.0-java)
     nokogiri (1.8.1)
       mini_portile2 (~> 2.3.0)
     nokogiri (1.8.1-java)
@@ -343,9 +335,9 @@ GEM
     nokogiri (1.8.1-x86-mingw32)
       mini_portile2 (~> 2.3.0)
     os (0.9.6)
-    parallel (1.12.0)
-    parser (2.4.0.0)
-      ast (~> 2.2)
+    parallel (1.12.1)
+    parser (2.5.0.2)
+      ast (~> 2.4.0)
     path_expander (1.0.2)
     pg (1.0.0)
     pg (1.0.0-x64-mingw32)
@@ -360,10 +352,10 @@ GEM
       selenium-webdriver
       thor
     racc (1.4.14)
-    rack (2.0.3)
+    rack (2.0.4)
     rack-cache (1.7.0)
       rack (>= 0.4)
-    rack-protection (2.0.0)
+    rack-protection (2.0.1)
       rack
     rack-test (0.8.0)
       rack (>= 1.0, < 3)
@@ -372,11 +364,10 @@ GEM
       nokogiri (>= 1.6)
     rails-html-sanitizer (1.0.3)
       loofah (~> 2.0)
-    rainbow (2.2.2)
-      rake
-    rake (12.2.1)
+    rainbow (3.0.0)
+    rake (12.3.0)
     rb-fsevent (0.10.2)
-    rdoc (5.1.0)
+    rdoc (6.0.1)
     redcarpet (3.2.3)
     redis (4.0.1)
     redis-namespace (1.6.0)
@@ -397,11 +388,11 @@ GEM
       resque (~> 1.26)
       rufus-scheduler (~> 3.2)
     retriable (3.1.1)
-    rubocop (0.51.0)
+    rubocop (0.52.1)
       parallel (~> 1.10)
-      parser (>= 2.3.3.1, < 3.0)
+      parser (>= 2.4.0.2, < 3.0)
       powerpack (~> 0.1)
-      rainbow (>= 2.2.2, < 3.0)
+      rainbow (>= 2.2.2, < 4.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
     ruby-progressbar (1.9.0)
@@ -421,6 +412,8 @@ GEM
       sprockets (>= 2.8, < 4.0)
       sprockets-rails (>= 2.0, < 4.0)
       tilt (>= 1.1, < 3)
+    sdoc (1.0.0)
+      rdoc (>= 5.0)
     selenium-webdriver (3.5.1)
       childprocess (~> 0.5)
       rubyzip (~> 1.0)
@@ -438,10 +431,10 @@ GEM
       faraday (~> 0.9)
       jwt (>= 1.5, < 3.0)
       multi_json (~> 1.10)
-    sinatra (2.0.0)
+    sinatra (2.0.1)
       mustermann (~> 1.0)
       rack (~> 2.0)
-      rack-protection (= 2.0.0)
+      rack-protection (= 2.0.1)
       tilt (~> 2.0)
     sneakers (2.5.0)
       bunny (~> 2.6.4)
@@ -524,6 +517,7 @@ DEPENDENCIES
   capybara (~> 2.15)
   chromedriver-helper
   coffee-rails
+  connection_pool
   dalli (>= 2.2.1)
   delayed_job
   delayed_job_active_record
@@ -536,7 +530,7 @@ DEPENDENCIES
   mini_magick
   minitest-bisect
   mocha
-  mysql2 (>= 0.4.4)
+  mysql2 (>= 0.4.10)
   nokogiri (>= 1.8.1)
   pg (>= 0.18.0)
   psych (~> 2.0)
@@ -556,7 +550,7 @@ DEPENDENCIES
   resque-scheduler
   rubocop (>= 0.47)
   sass-rails
-  sdoc!
+  sdoc (~> 1.0)
   sequel
   sidekiq
   sneakers
diff --git a/RAILS_VERSION b/RAILS_VERSION
index 5d41efd0ef..747766c587 100644
--- a/RAILS_VERSION
+++ b/RAILS_VERSION
@@ -1 +1 @@
-5.2.0.beta2
+6.0.0.alpha
diff --git a/actioncable/.gitignore b/actioncable/.gitignore
index 0a04b29786..f514e58c16 100644
--- a/actioncable/.gitignore
+++ b/actioncable/.gitignore
@@ -1,2 +1,2 @@
-/lib/assets/compiled
-/tmp
+/lib/assets/compiled/
+/tmp/
diff --git a/actioncable/CHANGELOG.md b/actioncable/CHANGELOG.md
index 38bf842b14..a28e2fe75d 100644
--- a/actioncable/CHANGELOG.md
+++ b/actioncable/CHANGELOG.md
@@ -1,34 +1,8 @@
-## Rails 5.2.0.beta2 (November 28, 2017) ##
+## Rails 6.0.0.alpha (Unreleased) ##
 
-*   No changes.
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Removed deprecated evented redis adapter.
-
-    *Rafael Mendonça França*
-
-*   Support redis-rb 4.0.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
     *Jeremy Daer*
 
-*   Hash long stream identifiers when using PostgreSQL adapter.
-
-    PostgreSQL has a limit on identifiers length (63 chars, [docs](https://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS)).
-    Provided fix minifies identifiers longer than 63 chars by hashing them with SHA1.
-
-    Fixes #28751.
-
-    *Vladimir Dementyev*
-
-*   Action Cable's `redis` adapter allows for other common redis-rb options (`host`, `port`, `db`, `password`) in cable.yml.
-
-    Previously, it accepts only a [redis:// url](https://www.iana.org/assignments/uri-schemes/prov/redis) as an option.
-    While we can add all of these options to the `url` itself, it is not explicitly documented. This alternative setup
-    is shown as the first example in the [Redis rubygem](https://github.com/redis/redis-rb#getting-started), which
-    makes this set of options as sensible as using just the `url`.
-
-    *Marc Rendl Ignacio*
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actioncable/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actioncable/CHANGELOG.md) for previous changes.
diff --git a/actioncable/actioncable.gemspec b/actioncable/actioncable.gemspec
index b5b98f1a6b..d946d0797f 100644
--- a/actioncable/actioncable.gemspec
+++ b/actioncable/actioncable.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "WebSocket framework for Rails."
   s.description = "Structure many real-time application concerns into channels over a single WebSocket connection."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -28,5 +28,5 @@ Gem::Specification.new do |s|
   s.add_dependency "actionpack", version
 
   s.add_dependency "nio4r",            "~> 2.0"
-  s.add_dependency "websocket-driver", "~> 0.6.1"
+  s.add_dependency "websocket-driver", ">= 0.6.1"
 end
diff --git a/actioncable/lib/action_cable/connection/base.rb b/actioncable/lib/action_cable/connection/base.rb
index 84053db9fd..11a1f1a5e8 100644
--- a/actioncable/lib/action_cable/connection/base.rb
+++ b/actioncable/lib/action_cable/connection/base.rb
@@ -136,13 +136,10 @@ module ActionCable
         send_async :handle_close
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :websocket
         attr_reader :message_buffer
 
-      private
         # The request that initiated the WebSocket connection is available here. This gives access to the environment, cookies, etc.
         def request # :doc:
           @request ||= begin
diff --git a/actioncable/lib/action_cable/connection/client_socket.rb b/actioncable/lib/action_cable/connection/client_socket.rb
index 10289ab55c..4b1964c4ae 100644
--- a/actioncable/lib/action_cable/connection/client_socket.rb
+++ b/actioncable/lib/action_cable/connection/client_socket.rb
@@ -83,7 +83,7 @@ module ActionCable
         when Numeric then @driver.text(message.to_s)
         when String  then @driver.text(message)
         when Array   then @driver.binary(message)
-          else false
+        else false
         end
       end
 
diff --git a/actioncable/lib/action_cable/connection/message_buffer.rb b/actioncable/lib/action_cable/connection/message_buffer.rb
index f151a47072..965841b67e 100644
--- a/actioncable/lib/action_cable/connection/message_buffer.rb
+++ b/actioncable/lib/action_cable/connection/message_buffer.rb
@@ -30,13 +30,10 @@ module ActionCable
         receive_buffered_messages
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :connection
         attr_reader :buffered_messages
 
-      private
         def valid?(message)
           message.is_a?(String)
         end
diff --git a/actioncable/lib/action_cable/connection/subscriptions.rb b/actioncable/lib/action_cable/connection/subscriptions.rb
index bb8d64e27a..1ad8d05107 100644
--- a/actioncable/lib/action_cable/connection/subscriptions.rb
+++ b/actioncable/lib/action_cable/connection/subscriptions.rb
@@ -63,12 +63,8 @@ module ActionCable
         subscriptions.each { |id, channel| remove_subscription(channel) }
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :connection, :subscriptions
-
       private
+        attr_reader :connection, :subscriptions
         delegate :logger, to: :connection
 
         def find(data)
diff --git a/actioncable/lib/action_cable/connection/web_socket.rb b/actioncable/lib/action_cable/connection/web_socket.rb
index 81233ace34..31f29fdd2f 100644
--- a/actioncable/lib/action_cable/connection/web_socket.rb
+++ b/actioncable/lib/action_cable/connection/web_socket.rb
@@ -34,9 +34,7 @@ module ActionCable
         websocket.rack_response
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :websocket
     end
   end
diff --git a/actioncable/lib/action_cable/gem_version.rb b/actioncable/lib/action_cable/gem_version.rb
index d72ba18acd..cd1d9bccef 100644
--- a/actioncable/lib/action_cable/gem_version.rb
+++ b/actioncable/lib/action_cable/gem_version.rb
@@ -7,10 +7,10 @@ module ActionCable
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actioncable/package.json b/actioncable/package.json
index 8d7f9ff302..d9df46043d 100644
--- a/actioncable/package.json
+++ b/actioncable/package.json
@@ -1,6 +1,6 @@
 {
   "name": "actioncable",
-  "version": "5.2.0-beta2",
+  "version": "6.0.0-alpha",
   "description": "WebSocket framework for Ruby on Rails.",
   "main": "lib/assets/compiled/action_cable.js",
   "files": [
diff --git a/actioncable/test/channel/base_test.rb b/actioncable/test/channel/base_test.rb
index 866bd7c21b..3b8eb63975 100644
--- a/actioncable/test/channel/base_test.rb
+++ b/actioncable/test/channel/base_test.rb
@@ -97,12 +97,12 @@ class ActionCable::Channel::BaseTest < ActiveSupport::TestCase
     @channel.subscribe_to_channel
 
     assert @channel.room
-    assert @channel.subscribed?
+    assert_predicate @channel, :subscribed?
 
     @channel.unsubscribe_from_channel
 
-    assert ! @channel.room
-    assert ! @channel.subscribed?
+    assert_not @channel.room
+    assert_not_predicate @channel, :subscribed?
   end
 
   test "connection identifiers" do
diff --git a/actioncable/test/channel/stream_test.rb b/actioncable/test/channel/stream_test.rb
index eca06fe365..e9e8849637 100644
--- a/actioncable/test/channel/stream_test.rb
+++ b/actioncable/test/channel/stream_test.rb
@@ -167,7 +167,7 @@ module ActionCable::StreamTests
 
         @server.broadcast "channel", {}
         wait_for_async
-        refute Thread.current[:ran_callback], "User callback was not run through the worker pool"
+        assert_not Thread.current[:ran_callback], "User callback was not run through the worker pool"
       end
     end
 
@@ -192,10 +192,10 @@ module ActionCable::StreamTests
 
         Connection.new(@server, env).tap do |connection|
           connection.process
-          assert connection.websocket.possible?
+          assert_predicate connection.websocket, :possible?
 
           wait_for_async
-          assert connection.websocket.alive?
+          assert_predicate connection.websocket, :alive?
         end
       end
 
diff --git a/actioncable/test/client_test.rb b/actioncable/test/client_test.rb
index 56b3ef143b..ec672a5828 100644
--- a/actioncable/test/client_test.rb
+++ b/actioncable/test/client_test.rb
@@ -307,7 +307,7 @@ class ClientTest < ActionCable::TestCase
 
       ActionCable.server.restart
       c.wait_for_close
-      assert c.closed?
+      assert_predicate c, :closed?
     end
   end
 end
diff --git a/actioncable/test/connection/base_test.rb b/actioncable/test/connection/base_test.rb
index 99488e38c8..c69d4d0b36 100644
--- a/actioncable/test/connection/base_test.rb
+++ b/actioncable/test/connection/base_test.rb
@@ -39,10 +39,10 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
       connection = open_connection
       connection.process
 
-      assert connection.websocket.possible?
+      assert_predicate connection.websocket, :possible?
 
       wait_for_async
-      assert connection.websocket.alive?
+      assert_predicate connection.websocket, :alive?
     end
   end
 
@@ -95,7 +95,7 @@ class ActionCable::Connection::BaseTest < ActionCable::TestCase
 
       statistics = connection.statistics
 
-      assert statistics[:identifier].blank?
+      assert_predicate statistics[:identifier], :blank?
       assert_kind_of Time, statistics[:started_at]
       assert_equal [], statistics[:subscriptions]
     end
diff --git a/actioncable/test/connection/subscriptions_test.rb b/actioncable/test/connection/subscriptions_test.rb
index 149a40604a..3323785494 100644
--- a/actioncable/test/connection/subscriptions_test.rb
+++ b/actioncable/test/connection/subscriptions_test.rb
@@ -45,7 +45,7 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       setup_connection
 
       @subscriptions.execute_command "command" => "subscribe"
-      assert @subscriptions.identifiers.empty?
+      assert_empty @subscriptions.identifiers
     end
   end
 
@@ -58,7 +58,7 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       channel.expects(:unsubscribe_from_channel)
 
       @subscriptions.execute_command "command" => "unsubscribe", "identifier" => @chat_identifier
-      assert @subscriptions.identifiers.empty?
+      assert_empty @subscriptions.identifiers
     end
   end
 
@@ -67,7 +67,7 @@ class ActionCable::Connection::SubscriptionsTest < ActionCable::TestCase
       setup_connection
 
       @subscriptions.execute_command "command" => "unsubscribe"
-      assert @subscriptions.identifiers.empty?
+      assert_empty @subscriptions.identifiers
     end
   end
 
diff --git a/actioncable/test/subscription_adapter/common.rb b/actioncable/test/subscription_adapter/common.rb
index c533a9f3eb..b3e9ae9d5c 100644
--- a/actioncable/test/subscription_adapter/common.rb
+++ b/actioncable/test/subscription_adapter/common.rb
@@ -32,7 +32,7 @@ module CommonSubscriptionAdapterTest
     subscribed = Concurrent::Event.new
     adapter.subscribe(channel, callback, Proc.new { subscribed.set })
     subscribed.wait(WAIT_WHEN_EXPECTING_EVENT)
-    assert subscribed.set?
+    assert_predicate subscribed, :set?
 
     yield queue
 
diff --git a/actionmailer/CHANGELOG.md b/actionmailer/CHANGELOG.md
index 2836f0cfbc..c5dbb0f1d4 100644
--- a/actionmailer/CHANGELOG.md
+++ b/actionmailer/CHANGELOG.md
@@ -1,27 +1,8 @@
-## Rails 5.2.0.beta2 (November 28, 2017) ##
+## Rails 6.0.0.alpha (Unreleased) ##
 
-*   No changes.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
+    *Jeremy Daer*
 
-## Rails 5.2.0.beta1 (November 27, 2017) ##
 
-*   Add `assert_enqueued_email_with` test helper.
-
-        assert_enqueued_email_with ContactMailer, :welcome do
-          ContactMailer.welcome.deliver_later
-        end
-
-    *Mikkel Malmberg*
-
-*   Allow Action Mailer classes to configure their delivery job.
-
-        class MyMailer < ApplicationMailer
-          self.delivery_job = MyCustomDeliveryJob
-
-          ...
-        end
-
-    *Matthew Mongeau*
-
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionmailer/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actionmailer/CHANGELOG.md) for previous changes.
diff --git a/actionmailer/actionmailer.gemspec b/actionmailer/actionmailer.gemspec
index b8a2e80bd3..f2fb160bdd 100644
--- a/actionmailer/actionmailer.gemspec
+++ b/actionmailer/actionmailer.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Email composition, delivery, and receiving framework (part of Rails)."
   s.description = "Email on Rails. Compose, deliver, receive, and test emails using the familiar controller/view pattern. First-class support for multipart email and attachments."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index eb8ae59533..3af95081ee 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -889,7 +889,7 @@ module ActionMailer
         default_values = self.class.default.map do |key, value|
           [
             key,
-            value.is_a?(Proc) ? instance_exec(&value) : value
+            compute_default(value)
           ]
         end.to_h
 
@@ -898,6 +898,16 @@ module ActionMailer
         headers_with_defaults
       end
 
+      def compute_default(value)
+        return value unless value.is_a?(Proc)
+
+        if value.arity == 1
+          instance_exec(self, &value)
+        else
+          instance_exec(&value)
+        end
+      end
+
       def assign_headers_to_message(message, headers)
         assignable = headers.except(:parts_order, :content_type, :body, :template_name,
                                     :template_path, :delivery_method, :delivery_method_options)
diff --git a/actionmailer/lib/action_mailer/gem_version.rb b/actionmailer/lib/action_mailer/gem_version.rb
index 6a7dd0a212..72eb5d61e8 100644
--- a/actionmailer/lib/action_mailer/gem_version.rb
+++ b/actionmailer/lib/action_mailer/gem_version.rb
@@ -7,10 +7,10 @@ module ActionMailer
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionmailer/test/base_test.rb b/actionmailer/test/base_test.rb
index 977e0e201e..4124aa00bd 100644
--- a/actionmailer/test/base_test.rb
+++ b/actionmailer/test/base_test.rb
@@ -506,8 +506,8 @@ class BaseTest < ActiveSupport::TestCase
   test "should respond to action methods" do
     assert_respond_to BaseMailer, :welcome
     assert_respond_to BaseMailer, :implicit_multipart
-    assert !BaseMailer.respond_to?(:mail)
-    assert !BaseMailer.respond_to?(:headers)
+    assert_not_respond_to BaseMailer, :mail
+    assert_not_respond_to BaseMailer, :headers
   end
 
   test "calling just the action should return the generated mail object" do
@@ -725,6 +725,15 @@ class BaseTest < ActiveSupport::TestCase
     assert(ProcMailer.welcome["x-has-to-proc"].to_s == "symbol")
   end
 
+  test "proc default values can have arity of 1 where arg is a mailer instance" do
+    assert_equal(ProcMailer.welcome["X-Lambda-Arity-1-arg"].to_s, "complex_value")
+    assert_equal(ProcMailer.welcome["X-Lambda-Arity-1-self"].to_s, "complex_value")
+  end
+
+  test "proc default values with fixed arity of 0 can be called" do
+    assert_equal("0", ProcMailer.welcome["X-Lambda-Arity-0"].to_s)
+  end
+
   test "we can call other defined methods on the class as needed" do
     mail = ProcMailer.welcome
     assert_equal("Thanks for signing up this afternoon", mail.subject)
diff --git a/actionmailer/test/caching_test.rb b/actionmailer/test/caching_test.rb
index ae4e7bf57e..574840c30e 100644
--- a/actionmailer/test/caching_test.rb
+++ b/actionmailer/test/caching_test.rb
@@ -105,7 +105,7 @@ class FragmentCachingTest < BaseCachingTest
 
     html_safe = @mailer.read_fragment("name")
     assert_equal content, html_safe
-    assert html_safe.html_safe?
+    assert_predicate html_safe, :html_safe?
   end
 end
 
@@ -262,7 +262,7 @@ class ViewCacheDependencyTest < BaseCachingTest
   end
 
   def test_view_cache_dependencies_are_empty_by_default
-    assert NoDependenciesMailer.new.view_cache_dependencies.empty?
+    assert_empty NoDependenciesMailer.new.view_cache_dependencies
   end
 
   def test_view_cache_dependencies_are_listed_in_declaration_order
diff --git a/actionmailer/test/mailers/proc_mailer.rb b/actionmailer/test/mailers/proc_mailer.rb
index b7cf53eb4a..76e730bb79 100644
--- a/actionmailer/test/mailers/proc_mailer.rb
+++ b/actionmailer/test/mailers/proc_mailer.rb
@@ -4,12 +4,19 @@ class ProcMailer < ActionMailer::Base
   default to: "system@test.lindsaar.net",
           "X-Proc-Method" => Proc.new { Time.now.to_i.to_s },
           subject: Proc.new { give_a_greeting },
-          "x-has-to-proc" => :symbol
+          "x-has-to-proc" => :symbol,
+          "X-Lambda-Arity-0" => ->() { "0" },
+          "X-Lambda-Arity-1-arg" => ->(arg) { arg.computed_value },
+          "X-Lambda-Arity-1-self" => ->(_) { self.computed_value }
 
   def welcome
     mail
   end
 
+  def computed_value
+    "complex_value"
+  end
+
   private
 
     def give_a_greeting
diff --git a/actionpack/CHANGELOG.md b/actionpack/CHANGELOG.md
index 6921f1b45f..98bf9c944b 100644
--- a/actionpack/CHANGELOG.md
+++ b/actionpack/CHANGELOG.md
@@ -1,252 +1,41 @@
-*   Update the default HSTS max-age value to 31536000 seconds (1 year)
-    to meet the minimum max-age requirement for https://hstspreload.org/.
+## Rails 6.0.0.alpha (Unreleased) ##
 
-    *Grant Bourque*
+*   Add support for automatic nonce generation for Rails UJS
 
-*   Add `Referrer-Policy` header to default headers set.
+    Because the UJS library creates a script tag to process responses it
+    normally requires the script-src attribute of the content security
+    policy to include 'unsafe-inline'.
 
-    *Guillermo Iguaran*
+    To work around this we generate a per-request nonce value that is
+    embedded in a meta tag in a similar fashion to how CSRF protection
+    embeds its token in a meta tag. The UJS library can then read the
+    nonce value and set it on the dynamically generated script tag to
+    enable it to execute without needing 'unsafe-inline' enabled.
 
-*   Changed the system tests to set Puma as default server only when the
-    user haven't specified manually another server.
+    Nonce generation isn't 100% safe - if your script tag is including
+    user generated content in someway then it may be possible to exploit
+    an XSS vulnerability which can take advantage of the nonce. It is
+    however an improvement on a blanket permission for inline scripts.
 
-    *Guillermo Iguaran*
+    It is also possible to use the nonce within your own script tags by
+    using `nonce: true` to set the nonce value on the tag, e.g
 
-*   Add secure `X-Download-Options` and `X-Permitted-Cross-Domain-Policies` to
-    default headers set.
+        <%= javascript_tag nonce: true do %>
+          alert('Hello, World!');
+        <% end %>
 
-    *Guillermo Iguaran*
-
-*   Add headless firefox support to System Tests.
-
-    *bogdanvlviv*
-
-*   Changed the default system test screenshot output from `inline` to `simple`.
-
-    `inline` works well for iTerm2 but not everyone uses iTerm2. Some terminals like
-    Terminal.app ignore the `inline` and output the path to the file since it can't
-    render the image. Other terminals, like those on Ubuntu, cannot handle the image
-    inline, but also don't handle it gracefully and instead of outputting the file
-    path, it dumps binary into the terminal.
-
-    Commit 9d6e28 fixes this by changing the default for screenshot to be `simple`.
-
-    *Eileen M. Uchitelle*
-
-*   Register most popular audio/video/font mime types supported by modern browsers.
-
-    *Guillermo Iguaran*
-
-*   Fix optimized url helpers when using relative url root
-
-    Fixes #31220.
+    Fixes #31689.
 
     *Andrew White*
 
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-## Rails 5.2.0.beta2 (November 28, 2017) ##
-
-*   No changes.
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Add DSL for configuring Content-Security-Policy header
-
-    The DSL allows you to configure a global Content-Security-Policy
-    header and then override within a controller. For more information
-    about the Content-Security-Policy header see MDN:
-
-    https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
-
-    Example global policy:
-
-        # config/initializers/content_security_policy.rb
-        Rails.application.config.content_security_policy do |p|
-          p.default_src :self, :https
-          p.font_src    :self, :https, :data
-          p.img_src     :self, :https, :data
-          p.object_src  :none
-          p.script_src  :self, :https
-          p.style_src   :self, :https, :unsafe_inline
-        end
-
-    Example controller overrides:
-
-        # Override policy inline
-        class PostsController < ApplicationController
-          content_security_policy do |p|
-            p.upgrade_insecure_requests true
-          end
-        end
-
-        # Using literal values
-        class PostsController < ApplicationController
-          content_security_policy do |p|
-            p.base_uri "https://www.example.com"
-          end
-        end
-
-        # Using mixed static and dynamic values
-        class PostsController < ApplicationController
-          content_security_policy do |p|
-            p.base_uri :self, -> { "https://#{current_user.domain}.example.com" }
-          end
-        end
-
-    Allows you to also only report content violations for migrating
-    legacy content using the `content_security_policy_report_only`
-    configuration attribute, e.g;
-
-        # config/initializers/content_security_policy.rb
-        Rails.application.config.content_security_policy_report_only = true
-
-        # controller override
-        class PostsController < ApplicationController
-          self.content_security_policy_report_only = true
-        end
-
-    Note that this feature does not validate the header for performance
-    reasons since the header is calculated at runtime.
-
-    *Andrew White*
-
-*   Make `assert_recognizes` to traverse mounted engines
-
-    *Yuichiro Kaneko*
-
-*   Remove deprecated `ActionController::ParamsParser::ParseError`.
-
-    *Rafael Mendonça França*
-
-*   Add `:allow_other_host` option to `redirect_back` method.
-
-    When `allow_other_host` is set to `false`, the `redirect_back` will not allow redirecting from a
-    different host. `allow_other_host` is `true` by default.
-
-    *Tim Masliuchenko*
-
-*   Add headless chrome support to System Tests.
-
-    *Yuji Yaginuma*
-
-*   Add ability to enable Early Hints for HTTP/2
-
-    If supported by the server, and enabled in Puma this allows H2 Early Hints to be used.
-
-    The `javascript_include_tag` and the `stylesheet_link_tag` automatically add Early Hints if requested.
-
-    *Eileen M. Uchitelle*, *Aaron Patterson*
-
-*   Simplify cookies middleware with key rotation support
-
-    Use the `rotate` method for both `MessageEncryptor` and
-    `MessageVerifier` to add key rotation support for encrypted and
-    signed cookies. This also helps simplify support for legacy cookie
-    security.
-
-    *Michael J Coyne*
-
-*   Use Capybara registered `:puma` server config.
-
-    The Capybara registered `:puma` server ensures the puma server is run in process so
-    connection sharing and open request detection work correctly by default.
-
-    *Thomas Walpole*
-
-*   Cookies `:expires` option supports `ActiveSupport::Duration` object.
-
-        cookies[:user_name] = { value: "assain", expires: 1.hour }
-        cookies[:key] = { value: "a yummy cookie", expires: 6.months }
-
-    Pull Request: #30121
-
-    *Assain Jaleel*
-
-*   Enforce signed/encrypted cookie expiry server side.
-
-    Rails can thwart attacks by malicious clients that don't honor a cookie's expiry.
-
-    It does so by stashing the expiry within the written cookie and relying on the
-    signing/encrypting to vouch that it hasn't been tampered with. Then on a
-    server-side read, the expiry is verified and any expired cookie is discarded.
-
-    Pull Request: #30121
-
-    *Assain Jaleel*
-
-*   Make `take_failed_screenshot` work within engine.
-
-    Fixes #30405.
-
-    *Yuji Yaginuma*
-
-*   Deprecate `ActionDispatch::TestResponse` response aliases.
-
-    `#success?`, `#missing?` & `#error?` are not supported by the actual
-    `ActionDispatch::Response` object and can produce false-positives. Instead,
-    use the response helpers provided by `Rack::Response`.
-
-    *Trevor Wistaff*
-
-*   Protect from forgery by default
-
-    Rather than protecting from forgery in the generated `ApplicationController`,
-    add it to `ActionController::Base` depending on
-    `config.action_controller.default_protect_from_forgery`. This configuration
-    defaults to false to support older versions which have removed it from their
-    `ApplicationController`, but is set to true for Rails 5.2.
-
-    *Lisa Ugray*
-
-*   Fallback `ActionController::Parameters#to_s` to `Hash#to_s`.
-
-    *Kir Shatrov*
-
-*   `driven_by` now registers poltergeist and capybara-webkit.
-
-    If poltergeist or capybara-webkit are set as drivers is set for System Tests,
-    `driven_by` will register the driver and set additional options passed via
-    the `:options` parameter.
-
-    Refer to the respective driver's documentation to see what options can be passed.
-
-    *Mario Chavez*
-
-*   AEAD encrypted cookies and sessions with GCM.
-
-    Encrypted cookies now use AES-GCM which couples authentication and
-    encryption in one faster step and produces shorter ciphertexts. Cookies
-    encrypted using AES in CBC HMAC mode will be seamlessly upgraded when
-    this new mode is enabled via the
-    `action_dispatch.use_authenticated_cookie_encryption` configuration value.
-
-    *Michael J Coyne*
-
-*   Change the cache key format for fragments to make it easier to debug key churn. The new format is:
-
-        views/template/action.html.erb:7a1156131a6928cb0026877f8b749ac9/projects/123
-              ^template path           ^template tree digest            ^class   ^id
-
-    *DHH*
-
-*   Add support for recyclable cache keys with fragment caching. This uses the new versioned entries in the
-    `ActiveSupport::Cache` stores and relies on the fact that Active Record has split `#cache_key` and `#cache_version`
-    to support it.
-
-    *DHH*
-
-*   Add `action_controller_api` and `action_controller_base` load hooks to be called in `ActiveSupport.on_load`
-
-    `ActionController::Base` and `ActionController::API` have differing implementations. This means that
-    the one umbrella hook `action_controller` is not able to address certain situations where a method
-    may not exist in a certain implementation.
-
-    This is fixed by adding two new hooks so you can target `ActionController::Base` vs `ActionController::API`
+    *Jeremy Daer*
 
-    Fixes #27013.
+*   Add alias method `to_hash` to `to_h` for `cookies`.
+    Add alias method `to_h` to `to_hash` for `session`.
 
-    *Julian Nadeau*
+    *Igor Kasyanchuk*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionpack/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actionpack/CHANGELOG.md) for previous changes.
diff --git a/actionpack/actionpack.gemspec b/actionpack/actionpack.gemspec
index 33d42e69d8..1dc8abf746 100644
--- a/actionpack/actionpack.gemspec
+++ b/actionpack/actionpack.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Web-flow and rendering framework putting the VC in MVC (part of Rails)."
   s.description = "Web apps on Rails. Simple, battle-tested conventions for building and testing MVC web applications. Works with any Rack-compatible server."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 457884ea08..f875aa5e6b 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -230,18 +230,16 @@ module ActionController
 
     # Returns a Rack endpoint for the given action name.
     def self.action(name)
+      app = lambda { |env|
+        req = ActionDispatch::Request.new(env)
+        res = make_response! req
+        new.dispatch(name, req, res)
+      }
+
       if middleware_stack.any?
-        middleware_stack.build(name) do |env|
-          req = ActionDispatch::Request.new(env)
-          res = make_response! req
-          new.dispatch(name, req, res)
-        end
+        middleware_stack.build(name, app)
       else
-        lambda { |env|
-          req = ActionDispatch::Request.new(env)
-          res = make_response! req
-          new.dispatch(name, req, res)
-        }
+        app
       end
     end
 
diff --git a/actionpack/lib/action_controller/metal/content_security_policy.rb b/actionpack/lib/action_controller/metal/content_security_policy.rb
index 48a7109bea..95f2f3242d 100644
--- a/actionpack/lib/action_controller/metal/content_security_policy.rb
+++ b/actionpack/lib/action_controller/metal/content_security_policy.rb
@@ -5,6 +5,14 @@ module ActionController #:nodoc:
     # TODO: Documentation
     extend ActiveSupport::Concern
 
+    include AbstractController::Helpers
+    include AbstractController::Callbacks
+
+    included do
+      helper_method :content_security_policy?
+      helper_method :content_security_policy_nonce
+    end
+
     module ClassMethods
       def content_security_policy(**options, &block)
         before_action(options) do
@@ -22,5 +30,15 @@ module ActionController #:nodoc:
         end
       end
     end
+
+    private
+
+      def content_security_policy?
+        request.content_security_policy
+      end
+
+      def content_security_policy_nonce
+        request.content_security_policy_nonce
+      end
   end
 end
diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
index 0ab313e398..94092de96c 100644
--- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb
+++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
@@ -3,7 +3,6 @@
 require "rack/session/abstract/id"
 require "action_controller/metal/exceptions"
 require "active_support/security_utils"
-require "active_support/core_ext/string/strip"
 
 module ActionController #:nodoc:
   class InvalidAuthenticityToken < ActionControllerError #:nodoc:
@@ -416,7 +415,7 @@ module ActionController #:nodoc:
         allow_forgery_protection
       end
 
-      NULL_ORIGIN_MESSAGE = <<-MSG.strip_heredoc
+      NULL_ORIGIN_MESSAGE = <<~MSG
         The browser returned a 'null' origin for a request with origin-based forgery protection turned on. This usually
         means you have the 'no-referrer' Referrer-Policy header enabled, or that you the request came from a site that
         refused to give its origin. This makes it impossible for Rails to verify the source of the requests. Likely the
diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index a56ac749f8..615c90c496 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/hash/indifferent_access"
-require "active_support/core_ext/hash/transform_values"
 require "active_support/core_ext/array/wrap"
 require "active_support/core_ext/string/filters"
 require "active_support/core_ext/object/to_query"
diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index 4b408750a4..798d142755 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -256,7 +256,7 @@ module ActionController
   #
   #   def test_create
   #     json = {book: { title: "Love Hina" }}.to_json
-  #     post :create, json
+  #     post :create, body: json
   #   end
   #
   # == Special instance variables
diff --git a/actionpack/lib/action_dispatch/http/content_security_policy.rb b/actionpack/lib/action_dispatch/http/content_security_policy.rb
index 4883e23d24..a3407c9698 100644
--- a/actionpack/lib/action_dispatch/http/content_security_policy.rb
+++ b/actionpack/lib/action_dispatch/http/content_security_policy.rb
@@ -21,6 +21,12 @@ module ActionDispatch #:nodoc:
         return response if policy_present?(headers)
 
         if policy = request.content_security_policy
+          if policy.directives["script-src"]
+            if nonce = request.content_security_policy_nonce
+              policy.directives["script-src"] << "'nonce-#{nonce}'"
+            end
+          end
+
           headers[header_name(request)] = policy.build(request.controller_instance)
         end
 
@@ -51,6 +57,8 @@ module ActionDispatch #:nodoc:
     module Request
       POLICY = "action_dispatch.content_security_policy".freeze
       POLICY_REPORT_ONLY = "action_dispatch.content_security_policy_report_only".freeze
+      NONCE_GENERATOR = "action_dispatch.content_security_policy_nonce_generator".freeze
+      NONCE = "action_dispatch.content_security_policy_nonce".freeze
 
       def content_security_policy
         get_header(POLICY)
@@ -67,6 +75,30 @@ module ActionDispatch #:nodoc:
       def content_security_policy_report_only=(value)
         set_header(POLICY_REPORT_ONLY, value)
       end
+
+      def content_security_policy_nonce_generator
+        get_header(NONCE_GENERATOR)
+      end
+
+      def content_security_policy_nonce_generator=(generator)
+        set_header(NONCE_GENERATOR, generator)
+      end
+
+      def content_security_policy_nonce
+        if content_security_policy_nonce_generator
+          if nonce = get_header(NONCE)
+            nonce
+          else
+            set_header(NONCE, generate_content_security_policy_nonce)
+          end
+        end
+      end
+
+      private
+
+        def generate_content_security_policy_nonce
+          content_security_policy_nonce_generator.call(self)
+        end
     end
 
     MAPPINGS = {
@@ -172,7 +204,7 @@ module ActionDispatch #:nodoc:
     end
 
     def build(context = nil)
-      build_directives(context).compact.join("; ") + ";"
+      build_directives(context).compact.join("; ")
     end
 
     private
diff --git a/actionpack/lib/action_dispatch/http/mime_type.rb b/actionpack/lib/action_dispatch/http/mime_type.rb
index d2b2106845..295539281f 100644
--- a/actionpack/lib/action_dispatch/http/mime_type.rb
+++ b/actionpack/lib/action_dispatch/http/mime_type.rb
@@ -279,8 +279,6 @@ module Mime
 
     def all?; false; end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
     protected
 
       attr_reader :string, :synonyms
diff --git a/actionpack/lib/action_dispatch/http/url.rb b/actionpack/lib/action_dispatch/http/url.rb
index f0344fd927..35ba44005a 100644
--- a/actionpack/lib/action_dispatch/http/url.rb
+++ b/actionpack/lib/action_dispatch/http/url.rb
@@ -274,7 +274,7 @@ module ActionDispatch
       def standard_port
         case protocol
         when "https://" then 443
-          else 80
+        else 80
         end
       end
 
diff --git a/actionpack/lib/action_dispatch/journey/nodes/node.rb b/actionpack/lib/action_dispatch/journey/nodes/node.rb
index 08b931a3cd..32f632800c 100644
--- a/actionpack/lib/action_dispatch/journey/nodes/node.rb
+++ b/actionpack/lib/action_dispatch/journey/nodes/node.rb
@@ -32,7 +32,7 @@ module ActionDispatch
         end
 
         def name
-          left.tr "*:".freeze, "".freeze
+          -left.tr("*:", "")
         end
 
         def type
@@ -82,7 +82,7 @@ module ActionDispatch
         def initialize(left)
           super
           @regexp = DEFAULT_EXP
-          @name = left.tr "*:".freeze, "".freeze
+          @name = -left.tr("*:", "")
         end
 
         def default_regexp?
diff --git a/actionpack/lib/action_dispatch/journey/path/pattern.rb b/actionpack/lib/action_dispatch/journey/path/pattern.rb
index 2d85a89a56..537f479ee5 100644
--- a/actionpack/lib/action_dispatch/journey/path/pattern.rb
+++ b/actionpack/lib/action_dispatch/journey/path/pattern.rb
@@ -90,7 +90,7 @@ module ActionDispatch
             return @separator_re unless @matchers.key?(node)
 
             re = @matchers[node]
-            "(#{re})"
+            "(#{Regexp.union(re)})"
           end
 
           def visit_GROUP(node)
@@ -183,7 +183,7 @@ module ActionDispatch
               node = node.to_sym
 
               if @requirements.key?(node)
-                re = /#{@requirements[node]}|/
+                re = /#{Regexp.union(@requirements[node])}|/
                 @offsets.push((re.match("").length - 1) + @offsets.last)
               else
                 @offsets << @offsets.last
diff --git a/actionpack/lib/action_dispatch/journey/scanner.rb b/actionpack/lib/action_dispatch/journey/scanner.rb
index 4ae77903fa..2a075862e9 100644
--- a/actionpack/lib/action_dispatch/journey/scanner.rb
+++ b/actionpack/lib/action_dispatch/journey/scanner.rb
@@ -34,6 +34,13 @@ module ActionDispatch
 
       private
 
+        # takes advantage of String @- deduping capabilities in Ruby 2.5 upwards
+        # see: https://bugs.ruby-lang.org/issues/13077
+        def dedup_scan(regex)
+          r = @ss.scan(regex)
+          r ? -r : nil
+        end
+
         def scan
           case
             # /
@@ -47,15 +54,15 @@ module ActionDispatch
             [:OR, "|"]
           when @ss.skip(/\./)
             [:DOT, "."]
-          when text = @ss.scan(/:\w+/)
+          when text = dedup_scan(/:\w+/)
             [:SYMBOL, text]
-          when text = @ss.scan(/\*\w+/)
+          when text = dedup_scan(/\*\w+/)
             [:STAR, text]
           when text = @ss.scan(/(?:[\w%\-~!$&'*+,;=@]|\\[:()])+/)
             text.tr! "\\", ""
-            [:LITERAL, text]
+            [:LITERAL, -text]
             # any char
-          when text = @ss.scan(/./)
+          when text = dedup_scan(/./)
             [:LITERAL, text]
           end
         end
diff --git a/actionpack/lib/action_dispatch/middleware/cookies.rb b/actionpack/lib/action_dispatch/middleware/cookies.rb
index ea4156c972..c45d947904 100644
--- a/actionpack/lib/action_dispatch/middleware/cookies.rb
+++ b/actionpack/lib/action_dispatch/middleware/cookies.rb
@@ -338,6 +338,9 @@ module ActionDispatch
       end
       alias :has_key? :key?
 
+      # Returns the cookies as Hash.
+      alias :to_hash :to_h
+
       def update(other_hash)
         @cookies.update other_hash.stringify_keys
         self
diff --git a/actionpack/lib/action_dispatch/middleware/request_id.rb b/actionpack/lib/action_dispatch/middleware/request_id.rb
index 805d3f2148..da2871b551 100644
--- a/actionpack/lib/action_dispatch/middleware/request_id.rb
+++ b/actionpack/lib/action_dispatch/middleware/request_id.rb
@@ -30,7 +30,7 @@ module ActionDispatch
     private
       def make_request_id(request_id)
         if request_id.presence
-          request_id.gsub(/[^\w\-]/, "".freeze).first(255)
+          request_id.gsub(/[^\w\-@]/, "".freeze).first(255)
         else
           internal_request_id
         end
diff --git a/actionpack/lib/action_dispatch/request/session.rb b/actionpack/lib/action_dispatch/request/session.rb
index d86d0b10c2..000847e193 100644
--- a/actionpack/lib/action_dispatch/request/session.rb
+++ b/actionpack/lib/action_dispatch/request/session.rb
@@ -130,6 +130,7 @@ module ActionDispatch
         load_for_read!
         @delegate.dup.delete_if { |_, v| v.nil? }
       end
+      alias :to_h :to_hash
 
       # Updates the session with given Hash.
       #
diff --git a/actionpack/lib/action_dispatch/routing/inspector.rb b/actionpack/lib/action_dispatch/routing/inspector.rb
index a2205569b4..22336c59b6 100644
--- a/actionpack/lib/action_dispatch/routing/inspector.rb
+++ b/actionpack/lib/action_dispatch/routing/inspector.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "delegate"
-require "active_support/core_ext/string/strip"
 
 module ActionDispatch
   module Routing
@@ -150,10 +149,10 @@ module ActionDispatch
       def no_routes(routes)
         @buffer <<
         if routes.none?
-          <<-MESSAGE.strip_heredoc
-          You don't have any routes defined!
+          <<~MESSAGE
+            You don't have any routes defined!
 
-          Please add some routes in config/routes.rb.
+            Please add some routes in config/routes.rb.
           MESSAGE
         else
           "No routes were found for this controller"
@@ -203,7 +202,7 @@ module ActionDispatch
       end
 
       def no_routes(*)
-        @buffer << <<-MESSAGE.strip_heredoc
+        @buffer << <<~MESSAGE
           <p>You don't have any routes defined!</p>
           <ul>
             <li>Please add some routes in <tt>config/routes.rb</tt>.</li>
diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index d87a23a58c..f3970d5445 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -611,7 +611,7 @@ module ActionDispatch
           end
 
           raise ArgumentError, "A rack application must be specified" unless app.respond_to?(:call)
-          raise ArgumentError, <<-MSG.strip_heredoc unless path
+          raise ArgumentError, <<~MSG unless path
             Must be called with mount point
 
               mount SomeRackApp, at: "some_route"
@@ -1573,7 +1573,7 @@ module ActionDispatch
         # Matches a URL pattern to one or more routes.
         # For more information, see match[rdoc-ref:Base#match].
         #
-        #   match 'path' => 'controller#action', via: patch
+        #   match 'path' => 'controller#action', via: :patch
         #   match 'path', to: 'controller#action', via: :post
         #   match 'path', 'otherpath', on: :member, via: :get
         def match(path, *rest, &block)
@@ -2082,9 +2082,9 @@ module ActionDispatch
         #     [ :products, options.merge(params.permit(:page, :size).to_h.symbolize_keys) ]
         #   end
         #
-        # In this instance the +params+ object comes from the context in which the the
+        # In this instance the +params+ object comes from the context in which the
         # block is executed, e.g. generating a URL inside a controller action or a view.
-        # If the block is executed where there isn't a params object such as this:
+        # If the block is executed where there isn't a +params+ object such as this:
         #
         #   Rails.application.routes.url_helpers.browse_path
         #
diff --git a/actionpack/lib/action_dispatch/routing/route_set.rb b/actionpack/lib/action_dispatch/routing/route_set.rb
index 9eff30fa53..a29a5a04ef 100644
--- a/actionpack/lib/action_dispatch/routing/route_set.rb
+++ b/actionpack/lib/action_dispatch/routing/route_set.rb
@@ -2,7 +2,6 @@
 
 require "action_dispatch/journey"
 require "active_support/core_ext/object/to_query"
-require "active_support/core_ext/hash/slice"
 require "active_support/core_ext/module/redefine_method"
 require "active_support/core_ext/module/remove_method"
 require "active_support/core_ext/array/extract_options"
@@ -154,13 +153,13 @@ module ActionDispatch
           url_name = :"#{name}_url"
 
           @path_helpers_module.module_eval do
-            define_method(path_name) do |*args|
+            redefine_method(path_name) do |*args|
               helper.call(self, args, true)
             end
           end
 
           @url_helpers_module.module_eval do
-            define_method(url_name) do |*args|
+            redefine_method(url_name) do |*args|
               helper.call(self, args, false)
             end
           end
@@ -855,7 +854,7 @@ module ActionDispatch
         recognize_path_with_request(req, path, extras)
       end
 
-      def recognize_path_with_request(req, path, extras)
+      def recognize_path_with_request(req, path, extras, raise_on_missing: true)
         @router.recognize(req) do |route, params|
           params.merge!(extras)
           params.each do |key, value|
@@ -875,12 +874,14 @@ module ActionDispatch
 
             return req.path_parameters
           elsif app.matches?(req) && app.engine?
-            path_parameters = app.rack_app.routes.recognize_path_with_request(req, path, extras)
-            return path_parameters
+            path_parameters = app.rack_app.routes.recognize_path_with_request(req, path, extras, raise_on_missing: false)
+            return path_parameters if path_parameters
           end
         end
 
-        raise ActionController::RoutingError, "No route matches #{path.inspect}"
+        if raise_on_missing
+          raise ActionController::RoutingError, "No route matches #{path.inspect}"
+        end
       end
     end
     # :startdoc:
diff --git a/actionpack/lib/action_dispatch/system_test_case.rb b/actionpack/lib/action_dispatch/system_test_case.rb
index 393141535b..f85f816bb9 100644
--- a/actionpack/lib/action_dispatch/system_test_case.rb
+++ b/actionpack/lib/action_dispatch/system_test_case.rb
@@ -6,6 +6,7 @@ require "capybara/dsl"
 require "capybara/minitest"
 require "action_controller"
 require "action_dispatch/system_testing/driver"
+require "action_dispatch/system_testing/browser"
 require "action_dispatch/system_testing/server"
 require "action_dispatch/system_testing/test_helpers/screenshot_helper"
 require "action_dispatch/system_testing/test_helpers/setup_and_teardown"
diff --git a/actionpack/lib/action_dispatch/system_testing/browser.rb b/actionpack/lib/action_dispatch/system_testing/browser.rb
new file mode 100644
index 0000000000..10e6888ab3
--- /dev/null
+++ b/actionpack/lib/action_dispatch/system_testing/browser.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module ActionDispatch
+  module SystemTesting
+    class Browser # :nodoc:
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+      end
+
+      def type
+        case name
+        when :headless_chrome
+          :chrome
+        when :headless_firefox
+          :firefox
+        else
+          name
+        end
+      end
+
+      def options
+        case name
+        when :headless_chrome
+          headless_chrome_browser_options
+        when :headless_firefox
+          headless_firefox_browser_options
+        end
+      end
+
+      private
+        def headless_chrome_browser_options
+          options = Selenium::WebDriver::Chrome::Options.new
+          options.args << "--headless"
+          options.args << "--disable-gpu"
+
+          options
+        end
+
+        def headless_firefox_browser_options
+          options = Selenium::WebDriver::Firefox::Options.new
+          options.args << "-headless"
+
+          options
+        end
+    end
+  end
+end
diff --git a/actionpack/lib/action_dispatch/system_testing/driver.rb b/actionpack/lib/action_dispatch/system_testing/driver.rb
index 280989a146..5252ff6746 100644
--- a/actionpack/lib/action_dispatch/system_testing/driver.rb
+++ b/actionpack/lib/action_dispatch/system_testing/driver.rb
@@ -5,7 +5,7 @@ module ActionDispatch
     class Driver # :nodoc:
       def initialize(name, **options)
         @name = name
-        @browser = options[:using]
+        @browser = Browser.new(options[:using])
         @screen_size = options[:screen_size]
         @options = options[:options]
       end
@@ -32,34 +32,11 @@ module ActionDispatch
         end
 
         def browser_options
-          if @browser == :headless_chrome
-            browser_options = Selenium::WebDriver::Chrome::Options.new
-            browser_options.args << "--headless"
-            browser_options.args << "--disable-gpu"
-
-            @options.merge(options: browser_options)
-          elsif @browser == :headless_firefox
-            browser_options = Selenium::WebDriver::Firefox::Options.new
-            browser_options.args << "-headless"
-
-            @options.merge(options: browser_options)
-          else
-            @options
-          end
-        end
-
-        def browser
-          if @browser == :headless_chrome
-            :chrome
-          elsif @browser == :headless_firefox
-            :firefox
-          else
-            @browser
-          end
+          @options.merge(options: @browser.options).compact
         end
 
         def register_selenium(app)
-          Capybara::Selenium::Driver.new(app, { browser: browser }.merge(browser_options)).tap do |driver|
+          Capybara::Selenium::Driver.new(app, { browser: @browser.type }.merge(browser_options)).tap do |driver|
             driver.browser.manage.window.size = Selenium::WebDriver::Dimension.new(*@screen_size)
           end
         end
diff --git a/actionpack/lib/action_pack/gem_version.rb b/actionpack/lib/action_pack/gem_version.rb
index 97f4934b58..37969fcb57 100644
--- a/actionpack/lib/action_pack/gem_version.rb
+++ b/actionpack/lib/action_pack/gem_version.rb
@@ -7,10 +7,10 @@ module ActionPack
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionpack/test/controller/action_pack_assertions_test.rb b/actionpack/test/controller/action_pack_assertions_test.rb
index f9a037e3cc..504c77b8ef 100644
--- a/actionpack/test/controller/action_pack_assertions_test.rb
+++ b/actionpack/test/controller/action_pack_assertions_test.rb
@@ -301,18 +301,18 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
   def test_empty_flash
     process :flash_me_naked
-    assert flash.empty?
+    assert_empty flash
   end
 
   def test_flash_exist
     process :flash_me
-    assert flash.any?
-    assert flash["hello"].present?
+    assert_predicate flash, :any?
+    assert_predicate flash["hello"], :present?
   end
 
   def test_flash_does_not_exist
     process :nothing
-    assert flash.empty?
+    assert_empty flash
   end
 
   def test_session_exist
@@ -322,7 +322,7 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
   def session_does_not_exist
     process :nothing
-    assert session.empty?
+    assert_empty session
   end
 
   def test_redirection_location
@@ -343,46 +343,46 @@ class ActionPackAssertionsControllerTest < ActionController::TestCase
 
   def test_server_error_response_code
     process :response500
-    assert @response.server_error?
+    assert_predicate @response, :server_error?
 
     process :response599
-    assert @response.server_error?
+    assert_predicate @response, :server_error?
 
     process :response404
-    assert !@response.server_error?
+    assert_not_predicate @response, :server_error?
   end
 
   def test_missing_response_code
     process :response404
-    assert @response.not_found?
+    assert_predicate @response, :not_found?
   end
 
   def test_client_error_response_code
     process :response404
-    assert @response.client_error?
+    assert_predicate @response, :client_error?
   end
 
   def test_redirect_url_match
     process :redirect_external
-    assert @response.redirect?
+    assert_predicate @response, :redirect?
     assert_match(/rubyonrails/, @response.redirect_url)
     assert !/perloffrails/.match(@response.redirect_url)
   end
 
   def test_redirection
     process :redirect_internal
-    assert @response.redirect?
+    assert_predicate @response, :redirect?
 
     process :redirect_external
-    assert @response.redirect?
+    assert_predicate @response, :redirect?
 
     process :nothing
-    assert !@response.redirect?
+    assert_not_predicate @response, :redirect?
   end
 
   def test_successful_response_code
     process :nothing
-    assert @response.successful?
+    assert_predicate @response, :successful?
   end
 
   def test_response_object
diff --git a/actionpack/test/controller/api/conditional_get_test.rb b/actionpack/test/controller/api/conditional_get_test.rb
index fd1997f26c..e366ce9532 100644
--- a/actionpack/test/controller/api/conditional_get_test.rb
+++ b/actionpack/test/controller/api/conditional_get_test.rb
@@ -53,7 +53,7 @@ class ConditionalGetApiTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :one
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 end
diff --git a/actionpack/test/controller/base_test.rb b/actionpack/test/controller/base_test.rb
index 9ac82c0d65..a672ede1a9 100644
--- a/actionpack/test/controller/base_test.rb
+++ b/actionpack/test/controller/base_test.rb
@@ -107,9 +107,9 @@ class ControllerInstanceTests < ActiveSupport::TestCase
   end
 
   def test_performed?
-    assert !@empty.performed?
+    assert_not_predicate @empty, :performed?
     @empty.response_body = ["sweet"]
-    assert @empty.performed?
+    assert_predicate @empty, :performed?
   end
 
   def test_action_methods
diff --git a/actionpack/test/controller/caching_test.rb b/actionpack/test/controller/caching_test.rb
index 3557f9f888..8b596083d5 100644
--- a/actionpack/test/controller/caching_test.rb
+++ b/actionpack/test/controller/caching_test.rb
@@ -159,7 +159,7 @@ class FragmentCachingTest < ActionController::TestCase
 
     html_safe = @controller.read_fragment("name")
     assert_equal content, html_safe
-    assert html_safe.html_safe?
+    assert_predicate html_safe, :html_safe?
   end
 end
 
@@ -382,7 +382,7 @@ class ViewCacheDependencyTest < ActionController::TestCase
   end
 
   def test_view_cache_dependencies_are_empty_by_default
-    assert NoDependenciesController.new.view_cache_dependencies.empty?
+    assert_empty NoDependenciesController.new.view_cache_dependencies
   end
 
   def test_view_cache_dependencies_are_listed_in_declaration_order
diff --git a/actionpack/test/controller/filters_test.rb b/actionpack/test/controller/filters_test.rb
index 9f0a9dec7a..2b16a555bb 100644
--- a/actionpack/test/controller/filters_test.rb
+++ b/actionpack/test/controller/filters_test.rb
@@ -819,7 +819,7 @@ class FilterTest < ActionController::TestCase
       response = test_process(RescuedController)
     end
 
-    assert response.successful?
+    assert_predicate response, :successful?
     assert_equal("I rescued this: #<FilterTest::ErrorToRescue: Something made the bad noise.>", response.body)
   end
 
diff --git a/actionpack/test/controller/flash_hash_test.rb b/actionpack/test/controller/flash_hash_test.rb
index f31a4d9329..6c3ac26de1 100644
--- a/actionpack/test/controller/flash_hash_test.rb
+++ b/actionpack/test/controller/flash_hash_test.rb
@@ -92,11 +92,11 @@ module ActionDispatch
     end
 
     def test_empty?
-      assert @hash.empty?
+      assert_empty @hash
       @hash["zomg"] = "bears"
-      assert !@hash.empty?
+      assert_not_empty @hash
       @hash.clear
-      assert @hash.empty?
+      assert_empty @hash
     end
 
     def test_each
diff --git a/actionpack/test/controller/http_digest_authentication_test.rb b/actionpack/test/controller/http_digest_authentication_test.rb
index 76ff784926..560157dc61 100644
--- a/actionpack/test/controller/http_digest_authentication_test.rb
+++ b/actionpack/test/controller/http_digest_authentication_test.rb
@@ -9,7 +9,7 @@ class HttpDigestAuthenticationTest < ActionController::TestCase
     before_action :authenticate_with_request, only: :display
 
     USERS = { "lifo" => "world", "pretty" => "please",
-              "dhh" => ::Digest::MD5::hexdigest(["dhh", "SuperSecret", "secret"].join(":")) }
+              "dhh" => ::Digest::MD5.hexdigest(["dhh", "SuperSecret", "secret"].join(":")) }
 
     def index
       render plain: "Hello Secret"
@@ -181,9 +181,10 @@ class HttpDigestAuthenticationTest < ActionController::TestCase
   end
 
   test "authentication request with password stored as ha1 digest hash" do
-    @request.env["HTTP_AUTHORIZATION"] = encode_credentials(username: "dhh",
-                                           password: ::Digest::MD5::hexdigest(["dhh", "SuperSecret", "secret"].join(":")),
-                                           password_is_ha1: true)
+    @request.env["HTTP_AUTHORIZATION"] = encode_credentials(
+      username: "dhh",
+      password: ::Digest::MD5.hexdigest(["dhh", "SuperSecret", "secret"].join(":")),
+      password_is_ha1: true)
     get :display
 
     assert_response :success
diff --git a/actionpack/test/controller/integration_test.rb b/actionpack/test/controller/integration_test.rb
index fd1c5e693f..a685f5868e 100644
--- a/actionpack/test/controller/integration_test.rb
+++ b/actionpack/test/controller/integration_test.rb
@@ -14,11 +14,11 @@ class SessionTest < ActiveSupport::TestCase
   end
 
   def test_https_bang_works_and_sets_truth_by_default
-    assert !@session.https?
+    assert_not_predicate @session, :https?
     @session.https!
-    assert @session.https?
+    assert_predicate @session, :https?
     @session.https! false
-    assert !@session.https?
+    assert_not_predicate @session, :https?
   end
 
   def test_host!
@@ -412,11 +412,11 @@ class IntegrationProcessTest < ActionDispatch::IntegrationTest
 
       get "/get_with_params", params: { foo: "bar" }
 
-      assert request.env["rack.input"].string.empty?
+      assert_empty request.env["rack.input"].string
       assert_equal "foo=bar", request.env["QUERY_STRING"]
       assert_equal "foo=bar", request.query_string
       assert_equal "bar", request.parameters["foo"]
-      assert request.parameters["leaks"].nil?
+      assert_predicate request.parameters["leaks"], :nil?
     end
   end
 
diff --git a/actionpack/test/controller/metal_test.rb b/actionpack/test/controller/metal_test.rb
index c3ebcb22b8..248ef36b7c 100644
--- a/actionpack/test/controller/metal_test.rb
+++ b/actionpack/test/controller/metal_test.rb
@@ -23,9 +23,9 @@ class MetalControllerInstanceTests < ActiveSupport::TestCase
       "rack.input" => -> {}
     )[1]
 
-    refute response_headers.key?("X-Frame-Options")
-    refute response_headers.key?("X-Content-Type-Options")
-    refute response_headers.key?("X-XSS-Protection")
+    assert_not response_headers.key?("X-Frame-Options")
+    assert_not response_headers.key?("X-Content-Type-Options")
+    assert_not response_headers.key?("X-XSS-Protection")
   ensure
     ActionDispatch::Response.default_headers = original_default_headers
   end
diff --git a/actionpack/test/controller/output_escaping_test.rb b/actionpack/test/controller/output_escaping_test.rb
index e33a99068f..d683bc73e6 100644
--- a/actionpack/test/controller/output_escaping_test.rb
+++ b/actionpack/test/controller/output_escaping_test.rb
@@ -4,7 +4,7 @@ require "abstract_unit"
 
 class OutputEscapingTest < ActiveSupport::TestCase
   test "escape_html shouldn't die when passed nil" do
-    assert ERB::Util.h(nil).blank?
+    assert_predicate ERB::Util.h(nil), :blank?
   end
 
   test "escapeHTML should escape strings" do
diff --git a/actionpack/test/controller/parameters/accessors_test.rb b/actionpack/test/controller/parameters/accessors_test.rb
index 154430d4b0..07a897a103 100644
--- a/actionpack/test/controller/parameters/accessors_test.rb
+++ b/actionpack/test/controller/parameters/accessors_test.rb
@@ -2,7 +2,6 @@
 
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
-require "active_support/core_ext/hash/transform_values"
 
 class ParametersAccessorsTest < ActiveSupport::TestCase
   setup do
@@ -22,13 +21,13 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "[] retains permitted status" do
     @params.permit!
-    assert @params[:person].permitted?
-    assert @params[:person][:name].permitted?
+    assert_predicate @params[:person], :permitted?
+    assert_predicate @params[:person][:name], :permitted?
   end
 
   test "[] retains unpermitted status" do
-    assert_not @params[:person].permitted?
-    assert_not @params[:person][:name].permitted?
+    assert_not_predicate @params[:person], :permitted?
+    assert_not_predicate @params[:person][:name], :permitted?
   end
 
   test "as_json returns the JSON representation of the parameters hash" do
@@ -78,33 +77,33 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "empty? returns true when params contains no key/value pairs" do
     params = ActionController::Parameters.new
-    assert params.empty?
+    assert_empty params
   end
 
   test "empty? returns false when any params are present" do
-    refute @params.empty?
+    assert_not_empty @params
   end
 
   test "except retains permitted status" do
     @params.permit!
-    assert @params.except(:person).permitted?
-    assert @params[:person].except(:name).permitted?
+    assert_predicate @params.except(:person), :permitted?
+    assert_predicate @params[:person].except(:name), :permitted?
   end
 
   test "except retains unpermitted status" do
-    assert_not @params.except(:person).permitted?
-    assert_not @params[:person].except(:name).permitted?
+    assert_not_predicate @params.except(:person), :permitted?
+    assert_not_predicate @params[:person].except(:name), :permitted?
   end
 
   test "fetch retains permitted status" do
     @params.permit!
-    assert @params.fetch(:person).permitted?
-    assert @params[:person].fetch(:name).permitted?
+    assert_predicate @params.fetch(:person), :permitted?
+    assert_predicate @params[:person].fetch(:name), :permitted?
   end
 
   test "fetch retains unpermitted status" do
-    assert_not @params.fetch(:person).permitted?
-    assert_not @params[:person].fetch(:name).permitted?
+    assert_not_predicate @params.fetch(:person), :permitted?
+    assert_not_predicate @params[:person].fetch(:name), :permitted?
   end
 
   test "has_key? returns true if the given key is present in the params" do
@@ -112,7 +111,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "has_key? returns false if the given key is not present in the params" do
-    refute @params.has_key?(:address)
+    assert_not @params.has_key?(:address)
   end
 
   test "has_value? returns true if the given value is present in the params" do
@@ -122,7 +121,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "has_value? returns false if the given value is not present in the params" do
     params = ActionController::Parameters.new(city: "Chicago", state: "Illinois")
-    refute params.has_value?("New York")
+    assert_not params.has_value?("New York")
   end
 
   test "include? returns true if the given key is present in the params" do
@@ -130,7 +129,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "include? returns false if the given key is not present in the params" do
-    refute @params.include?(:address)
+    assert_not @params.include?(:address)
   end
 
   test "key? returns true if the given key is present in the params" do
@@ -138,7 +137,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "key? returns false if the given key is not present in the params" do
-    refute @params.key?(:address)
+    assert_not @params.key?(:address)
   end
 
   test "keys returns an array of the keys of the params" do
@@ -147,48 +146,48 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
   end
 
   test "reject retains permitted status" do
-    assert_not @params.reject { |k| k == "person" }.permitted?
+    assert_not_predicate @params.reject { |k| k == "person" }, :permitted?
   end
 
   test "reject retains unpermitted status" do
     @params.permit!
-    assert @params.reject { |k| k == "person" }.permitted?
+    assert_predicate @params.reject { |k| k == "person" }, :permitted?
   end
 
   test "select retains permitted status" do
     @params.permit!
-    assert @params.select { |k| k == "person" }.permitted?
+    assert_predicate @params.select { |k| k == "person" }, :permitted?
   end
 
   test "select retains unpermitted status" do
-    assert_not @params.select { |k| k == "person" }.permitted?
+    assert_not_predicate @params.select { |k| k == "person" }, :permitted?
   end
 
   test "slice retains permitted status" do
     @params.permit!
-    assert @params.slice(:person).permitted?
+    assert_predicate @params.slice(:person), :permitted?
   end
 
   test "slice retains unpermitted status" do
-    assert_not @params.slice(:person).permitted?
+    assert_not_predicate @params.slice(:person), :permitted?
   end
 
   test "transform_keys retains permitted status" do
     @params.permit!
-    assert @params.transform_keys { |k| k }.permitted?
+    assert_predicate @params.transform_keys { |k| k }, :permitted?
   end
 
   test "transform_keys retains unpermitted status" do
-    assert_not @params.transform_keys { |k| k }.permitted?
+    assert_not_predicate @params.transform_keys { |k| k }, :permitted?
   end
 
   test "transform_values retains permitted status" do
     @params.permit!
-    assert @params.transform_values { |v| v }.permitted?
+    assert_predicate @params.transform_values { |v| v }, :permitted?
   end
 
   test "transform_values retains unpermitted status" do
-    assert_not @params.transform_values { |v| v }.permitted?
+    assert_not_predicate @params.transform_values { |v| v }, :permitted?
   end
 
   test "value? returns true if the given value is present in the params" do
@@ -198,7 +197,7 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "value? returns false if the given value is not present in the params" do
     params = ActionController::Parameters.new(city: "Chicago", state: "Illinois")
-    refute params.value?("New York")
+    assert_not params.value?("New York")
   end
 
   test "values returns an array of the values of the params" do
@@ -208,13 +207,13 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
 
   test "values_at retains permitted status" do
     @params.permit!
-    assert @params.values_at(:person).first.permitted?
-    assert @params[:person].values_at(:name).first.permitted?
+    assert_predicate @params.values_at(:person).first, :permitted?
+    assert_predicate @params[:person].values_at(:name).first, :permitted?
   end
 
   test "values_at retains unpermitted status" do
-    assert_not @params.values_at(:person).first.permitted?
-    assert_not @params[:person].values_at(:name).first.permitted?
+    assert_not_predicate @params.values_at(:person).first, :permitted?
+    assert_not_predicate @params[:person].values_at(:name).first, :permitted?
   end
 
   test "is equal to Parameters instance with same params" do
@@ -273,23 +272,16 @@ class ParametersAccessorsTest < ActiveSupport::TestCase
     assert_match(/permitted: true/, @params.inspect)
   end
 
-  if Hash.method_defined?(:dig)
-    test "#dig delegates the dig method to its values" do
-      assert_equal "David", @params.dig(:person, :name, :first)
-      assert_equal "Chicago", @params.dig(:person, :addresses, 0, :city)
-    end
+  test "#dig delegates the dig method to its values" do
+    assert_equal "David", @params.dig(:person, :name, :first)
+    assert_equal "Chicago", @params.dig(:person, :addresses, 0, :city)
+  end
 
-    test "#dig converts hashes to parameters" do
-      assert_kind_of ActionController::Parameters, @params.dig(:person)
-      assert_kind_of ActionController::Parameters, @params.dig(:person, :addresses, 0)
-      assert @params.dig(:person, :addresses).all? do |value|
-        value.is_a?(ActionController::Parameters)
-      end
-    end
-  else
-    test "ActionController::Parameters does not respond to #dig on Ruby 2.2" do
-      assert_not ActionController::Parameters.method_defined?(:dig)
-      assert_not @params.respond_to?(:dig)
+  test "#dig converts hashes to parameters" do
+    assert_kind_of ActionController::Parameters, @params.dig(:person)
+    assert_kind_of ActionController::Parameters, @params.dig(:person, :addresses, 0)
+    assert @params.dig(:person, :addresses).all? do |value|
+      value.is_a?(ActionController::Parameters)
     end
   end
 end
diff --git a/actionpack/test/controller/parameters/always_permitted_parameters_test.rb b/actionpack/test/controller/parameters/always_permitted_parameters_test.rb
index 1e8b71d789..fe0e5e368d 100644
--- a/actionpack/test/controller/parameters/always_permitted_parameters_test.rb
+++ b/actionpack/test/controller/parameters/always_permitted_parameters_test.rb
@@ -25,6 +25,6 @@ class AlwaysPermittedParametersTest < ActiveSupport::TestCase
       book: { pages: 65 },
       format: "json")
     permitted = params.permit book: [:pages]
-    assert permitted.permitted?
+    assert_predicate permitted, :permitted?
   end
 end
diff --git a/actionpack/test/controller/parameters/dup_test.rb b/actionpack/test/controller/parameters/dup_test.rb
index f5833aff46..5403fc6d93 100644
--- a/actionpack/test/controller/parameters/dup_test.rb
+++ b/actionpack/test/controller/parameters/dup_test.rb
@@ -23,7 +23,7 @@ class ParametersDupTest < ActiveSupport::TestCase
   test "a duplicate maintains the original's permitted status" do
     @params.permit!
     dupped_params = @params.dup
-    assert dupped_params.permitted?
+    assert_predicate dupped_params, :permitted?
   end
 
   test "a duplicate maintains the original's parameters" do
@@ -57,11 +57,11 @@ class ParametersDupTest < ActiveSupport::TestCase
     dupped_params = @params.deep_dup
     dupped_params.permit!
 
-    assert_not @params.permitted?
+    assert_not_predicate @params, :permitted?
   end
 
   test "deep_dup @permitted is being copied" do
     @params.permit!
-    assert @params.deep_dup.permitted?
+    assert_predicate @params.deep_dup, :permitted?
   end
 end
diff --git a/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb b/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb
index dcf848a620..c890839727 100644
--- a/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb
+++ b/actionpack/test/controller/parameters/multi_parameter_attributes_test.rb
@@ -21,7 +21,7 @@ class MultiParameterAttributesTest < ActiveSupport::TestCase
 
     permitted = params.permit book: [ :shipped_at, :price ]
 
-    assert permitted.permitted?
+    assert_predicate permitted, :permitted?
 
     assert_equal "2012", permitted[:book]["shipped_at(1i)"]
     assert_equal "3", permitted[:book]["shipped_at(2i)"]
diff --git a/actionpack/test/controller/parameters/mutators_test.rb b/actionpack/test/controller/parameters/mutators_test.rb
index 49dede03c2..312b1e5b27 100644
--- a/actionpack/test/controller/parameters/mutators_test.rb
+++ b/actionpack/test/controller/parameters/mutators_test.rb
@@ -2,7 +2,6 @@
 
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
-require "active_support/core_ext/hash/transform_values"
 
 class ParametersMutatorsTest < ActiveSupport::TestCase
   setup do
@@ -20,11 +19,11 @@ class ParametersMutatorsTest < ActiveSupport::TestCase
 
   test "delete retains permitted status" do
     @params.permit!
-    assert @params.delete(:person).permitted?
+    assert_predicate @params.delete(:person), :permitted?
   end
 
   test "delete retains unpermitted status" do
-    assert_not @params.delete(:person).permitted?
+    assert_not_predicate @params.delete(:person), :permitted?
   end
 
   test "delete returns the value when the key is present" do
@@ -50,73 +49,73 @@ class ParametersMutatorsTest < ActiveSupport::TestCase
 
   test "delete_if retains permitted status" do
     @params.permit!
-    assert @params.delete_if { |k| k == "person" }.permitted?
+    assert_predicate @params.delete_if { |k| k == "person" }, :permitted?
   end
 
   test "delete_if retains unpermitted status" do
-    assert_not @params.delete_if { |k| k == "person" }.permitted?
+    assert_not_predicate @params.delete_if { |k| k == "person" }, :permitted?
   end
 
   test "extract! retains permitted status" do
     @params.permit!
-    assert @params.extract!(:person).permitted?
+    assert_predicate @params.extract!(:person), :permitted?
   end
 
   test "extract! retains unpermitted status" do
-    assert_not @params.extract!(:person).permitted?
+    assert_not_predicate @params.extract!(:person), :permitted?
   end
 
   test "keep_if retains permitted status" do
     @params.permit!
-    assert @params.keep_if { |k, v| k == "person" }.permitted?
+    assert_predicate @params.keep_if { |k, v| k == "person" }, :permitted?
   end
 
   test "keep_if retains unpermitted status" do
-    assert_not @params.keep_if { |k, v| k == "person" }.permitted?
+    assert_not_predicate @params.keep_if { |k, v| k == "person" }, :permitted?
   end
 
   test "reject! retains permitted status" do
     @params.permit!
-    assert @params.reject! { |k| k == "person" }.permitted?
+    assert_predicate @params.reject! { |k| k == "person" }, :permitted?
   end
 
   test "reject! retains unpermitted status" do
-    assert_not @params.reject! { |k| k == "person" }.permitted?
+    assert_not_predicate @params.reject! { |k| k == "person" }, :permitted?
   end
 
   test "select! retains permitted status" do
     @params.permit!
-    assert @params.select! { |k| k != "person" }.permitted?
+    assert_predicate @params.select! { |k| k != "person" }, :permitted?
   end
 
   test "select! retains unpermitted status" do
-    assert_not @params.select! { |k| k != "person" }.permitted?
+    assert_not_predicate @params.select! { |k| k != "person" }, :permitted?
   end
 
   test "slice! retains permitted status" do
     @params.permit!
-    assert @params.slice!(:person).permitted?
+    assert_predicate @params.slice!(:person), :permitted?
   end
 
   test "slice! retains unpermitted status" do
-    assert_not @params.slice!(:person).permitted?
+    assert_not_predicate @params.slice!(:person), :permitted?
   end
 
   test "transform_keys! retains permitted status" do
     @params.permit!
-    assert @params.transform_keys! { |k| k }.permitted?
+    assert_predicate @params.transform_keys! { |k| k }, :permitted?
   end
 
   test "transform_keys! retains unpermitted status" do
-    assert_not @params.transform_keys! { |k| k }.permitted?
+    assert_not_predicate @params.transform_keys! { |k| k }, :permitted?
   end
 
   test "transform_values! retains permitted status" do
     @params.permit!
-    assert @params.transform_values! { |v| v }.permitted?
+    assert_predicate @params.transform_values! { |v| v }, :permitted?
   end
 
   test "transform_values! retains unpermitted status" do
-    assert_not @params.transform_values! { |v| v }.permitted?
+    assert_not_predicate @params.transform_values! { |v| v }, :permitted?
   end
 end
diff --git a/actionpack/test/controller/parameters/nested_parameters_permit_test.rb b/actionpack/test/controller/parameters/nested_parameters_permit_test.rb
index c9fcc483ee..ccc6bf9807 100644
--- a/actionpack/test/controller/parameters/nested_parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/nested_parameters_permit_test.rb
@@ -32,7 +32,7 @@ class NestedParametersPermitTest < ActiveSupport::TestCase
 
     permitted = params.permit book: [ :title, { authors: [ :name ] }, { details: :pages }, :id ]
 
-    assert permitted.permitted?
+    assert_predicate permitted, :permitted?
     assert_equal "Romeo and Juliet", permitted[:book][:title]
     assert_equal "William Shakespeare", permitted[:book][:authors][0][:name]
     assert_equal "Christopher Marlowe", permitted[:book][:authors][1][:name]
diff --git a/actionpack/test/controller/parameters/parameters_permit_test.rb b/actionpack/test/controller/parameters/parameters_permit_test.rb
index e9b94b056b..295f3a03ef 100644
--- a/actionpack/test/controller/parameters/parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/parameters_permit_test.rb
@@ -53,8 +53,8 @@ class ParametersPermitTest < ActiveSupport::TestCase
   test "if nothing is permitted, the hash becomes empty" do
     params = ActionController::Parameters.new(id: "1234")
     permitted = params.permit
-    assert permitted.permitted?
-    assert permitted.empty?
+    assert_predicate permitted, :permitted?
+    assert_empty permitted
   end
 
   test "key: permitted scalar values" do
@@ -227,7 +227,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
   test "hashes in array values get wrapped" do
     params = ActionController::Parameters.new(foo: [{}, {}])
     params[:foo].each do |hash|
-      assert !hash.permitted?
+      assert_not_predicate hash, :permitted?
     end
   end
 
@@ -250,7 +250,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
 
     permitted = params.permit(users: [:id])
     permitted[:users] << { injected: 1 }
-    assert_not permitted[:users].last.permitted?
+    assert_not_predicate permitted[:users].last, :permitted?
   end
 
   test "fetch doesnt raise ParameterMissing exception if there is a default" do
@@ -272,12 +272,12 @@ class ParametersPermitTest < ActiveSupport::TestCase
   end
 
   test "not permitted is sticky beyond merges" do
-    assert !@params.merge(a: "b").permitted?
+    assert_not_predicate @params.merge(a: "b"), :permitted?
   end
 
   test "permitted is sticky beyond merges" do
     @params.permit!
-    assert @params.merge(a: "b").permitted?
+    assert_predicate @params.merge(a: "b"), :permitted?
   end
 
   test "merge with parameters" do
@@ -288,12 +288,12 @@ class ParametersPermitTest < ActiveSupport::TestCase
   end
 
   test "not permitted is sticky beyond merge!" do
-    assert_not @params.merge!(a: "b").permitted?
+    assert_not_predicate @params.merge!(a: "b"), :permitted?
   end
 
   test "permitted is sticky beyond merge!" do
     @params.permit!
-    assert @params.merge!(a: "b").permitted?
+    assert_predicate @params.merge!(a: "b"), :permitted?
   end
 
   test "merge! with parameters" do
@@ -355,10 +355,10 @@ class ParametersPermitTest < ActiveSupport::TestCase
 
   test "permit is recursive" do
     @params.permit!
-    assert @params.permitted?
-    assert @params[:person].permitted?
-    assert @params[:person][:name].permitted?
-    assert @params[:person][:addresses][0].permitted?
+    assert_predicate @params, :permitted?
+    assert_predicate @params[:person], :permitted?
+    assert_predicate @params[:person][:name], :permitted?
+    assert_predicate @params[:person][:addresses][0], :permitted?
   end
 
   test "permitted takes a default value when Parameters.permit_all_parameters is set" do
@@ -368,8 +368,8 @@ class ParametersPermitTest < ActiveSupport::TestCase
         age: "32", name: { first: "David", last: "Heinemeier Hansson" }
       })
 
-      assert params.slice(:person).permitted?
-      assert params[:person][:name].permitted?
+      assert_predicate params.slice(:person), :permitted?
+      assert_predicate params[:person][:name], :permitted?
     ensure
       ActionController::Parameters.permit_all_parameters = false
     end
@@ -500,9 +500,9 @@ class ParametersPermitTest < ActiveSupport::TestCase
     params = ActionController::Parameters.new(foo: "bar")
 
     assert params.permit(:foo).has_key?(:foo)
-    refute params.permit(foo: []).has_key?(:foo)
-    refute params.permit(foo: [:bar]).has_key?(:foo)
-    refute params.permit(foo: :bar).has_key?(:foo)
+    assert_not params.permit(foo: []).has_key?(:foo)
+    assert_not params.permit(foo: [:bar]).has_key?(:foo)
+    assert_not params.permit(foo: :bar).has_key?(:foo)
   end
 
   test "#permitted? is false by default" do
diff --git a/actionpack/test/controller/parameters/serialization_test.rb b/actionpack/test/controller/parameters/serialization_test.rb
index 823f01d82a..7708c8e4fe 100644
--- a/actionpack/test/controller/parameters/serialization_test.rb
+++ b/actionpack/test/controller/parameters/serialization_test.rb
@@ -2,7 +2,6 @@
 
 require "abstract_unit"
 require "action_controller/metal/strong_parameters"
-require "active_support/core_ext/string/strip"
 
 class ParametersSerializationTest < ActiveSupport::TestCase
   setup do
@@ -27,21 +26,21 @@ class ParametersSerializationTest < ActiveSupport::TestCase
     roundtripped = YAML.load(YAML.dump(params))
 
     assert_equal params, roundtripped
-    assert_not roundtripped.permitted?
+    assert_not_predicate roundtripped, :permitted?
   end
 
   test "yaml backwardscompatible with psych 2.0.8 format" do
-    params = YAML.load <<-end_of_yaml.strip_heredoc
+    params = YAML.load <<~end_of_yaml
       --- !ruby/hash:ActionController::Parameters
       key: :value
     end_of_yaml
 
     assert_equal :value, params[:key]
-    assert_not params.permitted?
+    assert_not_predicate params, :permitted?
   end
 
   test "yaml backwardscompatible with psych 2.0.9+ format" do
-    params = YAML.load(<<-end_of_yaml.strip_heredoc)
+    params = YAML.load(<<~end_of_yaml)
       --- !ruby/hash-with-ivars:ActionController::Parameters
       elements:
         key: :value
@@ -50,6 +49,6 @@ class ParametersSerializationTest < ActiveSupport::TestCase
     end_of_yaml
 
     assert_equal :value, params[:key]
-    assert_not params.permitted?
+    assert_not_predicate params, :permitted?
   end
 end
diff --git a/actionpack/test/controller/render_test.rb b/actionpack/test/controller/render_test.rb
index 7c5101f993..fc21543049 100644
--- a/actionpack/test/controller/render_test.rb
+++ b/actionpack/test/controller/render_test.rb
@@ -415,7 +415,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :conditional_hello
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -430,7 +430,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = "Thu, 16 Jul 2008 00:00:00 GMT"
     get :conditional_hello
     assert_equal 200, @response.status.to_i
-    assert @response.body.present?
+    assert_predicate @response.body, :present?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -443,7 +443,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :conditional_hello_with_record
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_not_nil @response.etag
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
@@ -459,7 +459,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = "Thu, 16 Jul 2008 00:00:00 GMT"
     get :conditional_hello_with_record
     assert_equal 200, @response.status.to_i
-    assert @response.body.present?
+    assert_predicate @response.body, :present?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -472,7 +472,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = @last_modified
     get :conditional_hello_with_collection_of_records
     assert_equal 304, @response.status.to_i
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -487,7 +487,7 @@ class LastModifiedRenderTest < ActionController::TestCase
     @request.if_modified_since = "Thu, 16 Jul 2008 00:00:00 GMT"
     get :conditional_hello_with_collection_of_records
     assert_equal 200, @response.status.to_i
-    assert @response.body.present?
+    assert_predicate @response.body, :present?
     assert_equal @last_modified, @response.headers["Last-Modified"]
   end
 
@@ -682,27 +682,27 @@ class HeadRenderTest < ActionController::TestCase
 
   def test_head_created
     post :head_created
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_response :created
   end
 
   def test_head_created_with_application_json_content_type
     post :head_created_with_application_json_content_type
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "application/json", @response.header["Content-Type"]
     assert_response :created
   end
 
   def test_head_ok_with_image_png_content_type
     post :head_ok_with_image_png_content_type
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "image/png", @response.header["Content-Type"]
     assert_response :ok
   end
 
   def test_head_with_location_header
     get :head_with_location_header
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "/foo", @response.headers["Location"]
     assert_response :ok
   end
@@ -718,7 +718,7 @@ class HeadRenderTest < ActionController::TestCase
       end
 
       get :head_with_location_object
-      assert @response.body.blank?
+      assert_predicate @response.body, :blank?
       assert_equal "http://www.nextangle.com/customers/1", @response.headers["Location"]
       assert_response :ok
     end
@@ -726,14 +726,14 @@ class HeadRenderTest < ActionController::TestCase
 
   def test_head_with_custom_header
     get :head_with_custom_header
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "something", @response.headers["X-Custom-Header"]
     assert_response :ok
   end
 
   def test_head_with_www_authenticate_header
     get :head_with_www_authenticate_header
-    assert @response.body.blank?
+    assert_predicate @response.body, :blank?
     assert_equal "something", @response.headers["WWW-Authenticate"]
     assert_response :ok
   end
@@ -812,7 +812,7 @@ class HttpCacheForeverTest < ActionController::TestCase
     assert_response :ok
     assert_equal "max-age=#{100.years}, public", @response.headers["Cache-Control"]
     assert_not_nil @response.etag
-    assert @response.weak_etag?
+    assert_predicate @response, :weak_etag?
   end
 
   def test_cache_with_private
@@ -820,7 +820,7 @@ class HttpCacheForeverTest < ActionController::TestCase
     assert_response :ok
     assert_equal "max-age=#{100.years}, private", @response.headers["Cache-Control"]
     assert_not_nil @response.etag
-    assert @response.weak_etag?
+    assert_predicate @response, :weak_etag?
   end
 
   def test_cache_response_code_with_if_modified_since
diff --git a/actionpack/test/controller/request_forgery_protection_test.rb b/actionpack/test/controller/request_forgery_protection_test.rb
index 4822d85bcb..7a02c27c99 100644
--- a/actionpack/test/controller/request_forgery_protection_test.rb
+++ b/actionpack/test/controller/request_forgery_protection_test.rb
@@ -746,7 +746,7 @@ class FreeCookieControllerTest < ActionController::TestCase
   test "should not emit a csrf-token meta tag" do
     SecureRandom.stub :base64, @token do
       get :meta
-      assert @response.body.blank?
+      assert_predicate @response.body, :blank?
     end
   end
 end
diff --git a/actionpack/test/controller/routing_test.rb b/actionpack/test/controller/routing_test.rb
index ec939e946a..9c0e101f7c 100644
--- a/actionpack/test/controller/routing_test.rb
+++ b/actionpack/test/controller/routing_test.rb
@@ -676,7 +676,7 @@ class LegacyRouteSetTests < ActiveSupport::TestCase
 
     token = "\321\202\320\265\320\272\321\201\321\202".dup # 'text' in Russian
     token.force_encoding(Encoding::BINARY)
-    escaped_token = CGI::escape(token)
+    escaped_token = CGI.escape(token)
 
     assert_equal "/page/" + escaped_token, url_for(rs, controller: "content", action: "show_page", id: token)
     assert_equal({ controller: "content", action: "show_page", id: token }, rs.recognize_path("/page/#{escaped_token}"))
diff --git a/actionpack/test/controller/runner_test.rb b/actionpack/test/controller/runner_test.rb
index a96c9c519b..1709ab5f6d 100644
--- a/actionpack/test/controller/runner_test.rb
+++ b/actionpack/test/controller/runner_test.rb
@@ -17,8 +17,8 @@ module ActionDispatch
 
     def test_respond_to?
       runner = MyRunner.new(Class.new { def x; end }.new)
-      assert runner.respond_to?(:hi)
-      assert runner.respond_to?(:x)
+      assert_respond_to runner, :hi
+      assert_respond_to runner, :x
     end
   end
 end
diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index 536c5ed97a..7d4850294d 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -670,7 +670,7 @@ XML
     assert_equal "bar", @request.params[:foo]
 
     post :no_op
-    assert @request.params[:foo].blank?
+    assert_predicate @request.params[:foo], :blank?
   end
 
   def test_filtered_parameters_reset_between_requests
@@ -838,7 +838,7 @@ XML
 
   def test_fixture_file_upload_should_be_able_access_to_tempfile
     file = fixture_file_upload(FILES_DIR + "/ruby_on_rails.jpg", "image/jpg")
-    assert file.respond_to?(:tempfile), "expected tempfile should respond on fixture file object, got nothing"
+    assert_respond_to file, :tempfile
   end
 
   def test_fixture_file_upload
diff --git a/actionpack/test/controller/url_for_test.rb b/actionpack/test/controller/url_for_test.rb
index cf11227897..e381abee36 100644
--- a/actionpack/test/controller/url_for_test.rb
+++ b/actionpack/test/controller/url_for_test.rb
@@ -288,7 +288,7 @@ module AbstractController
           kls = Class.new { include set.url_helpers }
 
           controller = kls.new
-          assert controller.respond_to?(:home_url)
+          assert_respond_to controller, :home_url
           assert_equal "http://www.basecamphq.com/home/sweet/home/again",
             controller.send(:home_url, host: "www.basecamphq.com", user: "again")
 
diff --git a/actionpack/test/dispatch/content_security_policy_test.rb b/actionpack/test/dispatch/content_security_policy_test.rb
index 7c4a65a633..b88f90190a 100644
--- a/actionpack/test/dispatch/content_security_policy_test.rb
+++ b/actionpack/test/dispatch/content_security_policy_test.rb
@@ -8,10 +8,10 @@ class ContentSecurityPolicyTest < ActiveSupport::TestCase
   end
 
   def test_build
-    assert_equal ";", @policy.build
+    assert_equal "", @policy.build
 
     @policy.script_src :self
-    assert_equal "script-src 'self';", @policy.build
+    assert_equal "script-src 'self'", @policy.build
   end
 
   def test_dup
@@ -25,34 +25,34 @@ class ContentSecurityPolicyTest < ActiveSupport::TestCase
 
   def test_mappings
     @policy.script_src :data
-    assert_equal "script-src data:;", @policy.build
+    assert_equal "script-src data:", @policy.build
 
     @policy.script_src :mediastream
-    assert_equal "script-src mediastream:;", @policy.build
+    assert_equal "script-src mediastream:", @policy.build
 
     @policy.script_src :blob
-    assert_equal "script-src blob:;", @policy.build
+    assert_equal "script-src blob:", @policy.build
 
     @policy.script_src :filesystem
-    assert_equal "script-src filesystem:;", @policy.build
+    assert_equal "script-src filesystem:", @policy.build
 
     @policy.script_src :self
-    assert_equal "script-src 'self';", @policy.build
+    assert_equal "script-src 'self'", @policy.build
 
     @policy.script_src :unsafe_inline
-    assert_equal "script-src 'unsafe-inline';", @policy.build
+    assert_equal "script-src 'unsafe-inline'", @policy.build
 
     @policy.script_src :unsafe_eval
-    assert_equal "script-src 'unsafe-eval';", @policy.build
+    assert_equal "script-src 'unsafe-eval'", @policy.build
 
     @policy.script_src :none
-    assert_equal "script-src 'none';", @policy.build
+    assert_equal "script-src 'none'", @policy.build
 
     @policy.script_src :strict_dynamic
-    assert_equal "script-src 'strict-dynamic';", @policy.build
+    assert_equal "script-src 'strict-dynamic'", @policy.build
 
     @policy.script_src :none, :report_sample
-    assert_equal "script-src 'none' 'report-sample';", @policy.build
+    assert_equal "script-src 'none' 'report-sample'", @policy.build
   end
 
   def test_fetch_directives
@@ -131,16 +131,16 @@ class ContentSecurityPolicyTest < ActiveSupport::TestCase
 
   def test_document_directives
     @policy.base_uri "https://example.com"
-    assert_match %r{base-uri https://example\.com;}, @policy.build
+    assert_match %r{base-uri https://example\.com}, @policy.build
 
     @policy.plugin_types "application/x-shockwave-flash"
-    assert_match %r{plugin-types application/x-shockwave-flash;}, @policy.build
+    assert_match %r{plugin-types application/x-shockwave-flash}, @policy.build
 
     @policy.sandbox
-    assert_match %r{sandbox;}, @policy.build
+    assert_match %r{sandbox}, @policy.build
 
     @policy.sandbox "allow-scripts", "allow-modals"
-    assert_match %r{sandbox allow-scripts allow-modals;}, @policy.build
+    assert_match %r{sandbox allow-scripts allow-modals}, @policy.build
 
     @policy.sandbox false
     assert_no_match %r{sandbox}, @policy.build
@@ -148,35 +148,35 @@ class ContentSecurityPolicyTest < ActiveSupport::TestCase
 
   def test_navigation_directives
     @policy.form_action :self
-    assert_match %r{form-action 'self';}, @policy.build
+    assert_match %r{form-action 'self'}, @policy.build
 
     @policy.frame_ancestors :self
-    assert_match %r{frame-ancestors 'self';}, @policy.build
+    assert_match %r{frame-ancestors 'self'}, @policy.build
   end
 
   def test_reporting_directives
     @policy.report_uri "/violations"
-    assert_match %r{report-uri /violations;}, @policy.build
+    assert_match %r{report-uri /violations}, @policy.build
   end
 
   def test_other_directives
     @policy.block_all_mixed_content
-    assert_match %r{block-all-mixed-content;}, @policy.build
+    assert_match %r{block-all-mixed-content}, @policy.build
 
     @policy.block_all_mixed_content false
     assert_no_match %r{block-all-mixed-content}, @policy.build
 
     @policy.require_sri_for :script, :style
-    assert_match %r{require-sri-for script style;}, @policy.build
+    assert_match %r{require-sri-for script style}, @policy.build
 
     @policy.require_sri_for "script", "style"
-    assert_match %r{require-sri-for script style;}, @policy.build
+    assert_match %r{require-sri-for script style}, @policy.build
 
     @policy.require_sri_for
     assert_no_match %r{require-sri-for}, @policy.build
 
     @policy.upgrade_insecure_requests
-    assert_match %r{upgrade-insecure-requests;}, @policy.build
+    assert_match %r{upgrade-insecure-requests}, @policy.build
 
     @policy.upgrade_insecure_requests false
     assert_no_match %r{upgrade-insecure-requests}, @policy.build
@@ -184,13 +184,13 @@ class ContentSecurityPolicyTest < ActiveSupport::TestCase
 
   def test_multiple_sources
     @policy.script_src :self, :https
-    assert_equal "script-src 'self' https:;", @policy.build
+    assert_equal "script-src 'self' https:", @policy.build
   end
 
   def test_multiple_directives
     @policy.script_src :self, :https
     @policy.style_src :self, :https
-    assert_equal "script-src 'self' https:; style-src 'self' https:;", @policy.build
+    assert_equal "script-src 'self' https:; style-src 'self' https:", @policy.build
   end
 
   def test_dynamic_directives
@@ -198,12 +198,12 @@ class ContentSecurityPolicyTest < ActiveSupport::TestCase
     controller = Struct.new(:request).new(request)
 
     @policy.script_src -> { request.host }
-    assert_equal "script-src www.example.com;", @policy.build(controller)
+    assert_equal "script-src www.example.com", @policy.build(controller)
   end
 
   def test_mixed_static_and_dynamic_directives
     @policy.script_src :self, -> { "foo.com" }, "bar.com"
-    assert_equal "script-src 'self' foo.com bar.com;", @policy.build(Object.new)
+    assert_equal "script-src 'self' foo.com bar.com", @policy.build(Object.new)
   end
 
   def test_invalid_directive_source
@@ -253,6 +253,11 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
       p.report_uri "/violations"
     end
 
+    content_security_policy only: :script_src do |p|
+      p.default_src false
+      p.script_src :self
+    end
+
     content_security_policy_report_only only: :report_only
 
     def index
@@ -271,6 +276,10 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
       head :ok
     end
 
+    def script_src
+      head :ok
+    end
+
     private
       def condition?
         params[:condition] == "true"
@@ -284,6 +293,7 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
       get "/inline", to: "policy#inline"
       get "/conditional", to: "policy#conditional"
       get "/report-only", to: "policy#report_only"
+      get "/script-src", to: "policy#script_src"
     end
   end
 
@@ -298,6 +308,7 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
 
     def call(env)
       env["action_dispatch.content_security_policy"] = POLICY
+      env["action_dispatch.content_security_policy_nonce_generator"] = proc { "iyhD0Yc0W+c=" }
       env["action_dispatch.content_security_policy_report_only"] = false
       env["action_dispatch.show_exceptions"] = false
 
@@ -316,25 +327,30 @@ class ContentSecurityPolicyIntegrationTest < ActionDispatch::IntegrationTest
 
   def test_generates_content_security_policy_header
     get "/"
-    assert_policy "default-src 'self';"
+    assert_policy "default-src 'self'"
   end
 
   def test_generates_inline_content_security_policy
     get "/inline"
-    assert_policy "default-src https://example.com;"
+    assert_policy "default-src https://example.com"
   end
 
   def test_generates_conditional_content_security_policy
     get "/conditional", params: { condition: "true" }
-    assert_policy "default-src https://true.example.com;"
+    assert_policy "default-src https://true.example.com"
 
     get "/conditional", params: { condition: "false" }
-    assert_policy "default-src https://false.example.com;"
+    assert_policy "default-src https://false.example.com"
   end
 
   def test_generates_report_only_content_security_policy
     get "/report-only"
-    assert_policy "default-src 'self'; report-uri /violations;", report_only: true
+    assert_policy "default-src 'self'; report-uri /violations", report_only: true
+  end
+
+  def test_adds_nonce_to_script_src_content_security_policy
+    get "/script-src"
+    assert_policy "script-src 'self' 'nonce-iyhD0Yc0W+c='"
   end
 
   private
diff --git a/actionpack/test/dispatch/cookies_test.rb b/actionpack/test/dispatch/cookies_test.rb
index 40cbad3b0d..94cff10fe4 100644
--- a/actionpack/test/dispatch/cookies_test.rb
+++ b/actionpack/test/dispatch/cookies_test.rb
@@ -36,6 +36,12 @@ class CookieJarTest < ActiveSupport::TestCase
     assert_equal "bar", request.cookie_jar.fetch(:foo)
   end
 
+  def test_to_hash
+    request.cookie_jar["foo"] = "bar"
+    assert_equal({ "foo" => "bar" }, request.cookie_jar.to_hash)
+    assert_equal({ "foo" => "bar" }, request.cookie_jar.to_h)
+  end
+
   def test_fetch_type_error
     assert_raises(KeyError) do
       request.cookie_jar.fetch(:omglolwut)
@@ -319,7 +325,7 @@ class CookiesTest < ActionController::TestCase
   def test_setting_the_same_value_to_cookie
     request.cookies[:user_name] = "david"
     get :authenticate
-    assert_predicate response.cookies, :empty?
+    assert_empty response.cookies
   end
 
   def test_setting_the_same_value_to_permanent_cookie
@@ -401,7 +407,7 @@ class CookiesTest < ActionController::TestCase
   def test_delete_unexisting_cookie
     request.cookies.clear
     get :delete_cookie
-    assert_predicate @response.cookies, :empty?
+    assert_empty @response.cookies
   end
 
   def test_deleted_cookie_predicate
diff --git a/actionpack/test/dispatch/live_response_test.rb b/actionpack/test/dispatch/live_response_test.rb
index 2901148a9e..a9a56f205f 100644
--- a/actionpack/test/dispatch/live_response_test.rb
+++ b/actionpack/test/dispatch/live_response_test.rb
@@ -73,7 +73,7 @@ module ActionController
         }
 
         latch.wait
-        assert @response.headers.frozen?
+        assert_predicate @response.headers, :frozen?
         e = assert_raises(ActionDispatch::IllegalStateError) do
           @response.headers["Content-Length"] = "zomg"
         end
diff --git a/actionpack/test/dispatch/mime_type_test.rb b/actionpack/test/dispatch/mime_type_test.rb
index 6854783386..6167ea46df 100644
--- a/actionpack/test/dispatch/mime_type_test.rb
+++ b/actionpack/test/dispatch/mime_type_test.rb
@@ -159,7 +159,7 @@ class MimeTypeTest < ActiveSupport::TestCase
 
     types.each do |type|
       mime = Mime[type]
-      assert mime.respond_to?("#{type}?"), "#{mime.inspect} does not respond to #{type}?"
+      assert_respond_to mime, "#{type}?"
       assert_equal type, mime.symbol, "#{mime.inspect} is not #{type}?"
       invalid_types = types - [type]
       invalid_types.delete(:html)
diff --git a/actionpack/test/dispatch/request/session_test.rb b/actionpack/test/dispatch/request/session_test.rb
index 7b6ce31f29..bf5a74e694 100644
--- a/actionpack/test/dispatch/request/session_test.rb
+++ b/actionpack/test/dispatch/request/session_test.rb
@@ -22,6 +22,7 @@ module ActionDispatch
         s["foo"] = "bar"
         assert_equal "bar", s["foo"]
         assert_equal({ "foo" => "bar" }, s.to_hash)
+        assert_equal({ "foo" => "bar" }, s.to_h)
       end
 
       def test_create_merges_old
diff --git a/actionpack/test/dispatch/request_id_test.rb b/actionpack/test/dispatch/request_id_test.rb
index aa3175c986..9df4712dab 100644
--- a/actionpack/test/dispatch/request_id_test.rb
+++ b/actionpack/test/dispatch/request_id_test.rb
@@ -11,6 +11,11 @@ class RequestIdTest < ActiveSupport::TestCase
     assert_equal "X-Hacked-HeaderStuff", stub_request("HTTP_X_REQUEST_ID" => "; X-Hacked-Header: Stuff").request_id
   end
 
+  test "accept Apache mod_unique_id format" do
+    mod_unique_id = "abcxyz@ABCXYZ-0123456789"
+    assert_equal mod_unique_id, stub_request("HTTP_X_REQUEST_ID" => mod_unique_id).request_id
+  end
+
   test "ensure that 255 char limit on the request id is being enforced" do
     assert_equal "X" * 255, stub_request("HTTP_X_REQUEST_ID" => "X" * 500).request_id
   end
diff --git a/actionpack/test/dispatch/request_test.rb b/actionpack/test/dispatch/request_test.rb
index 66736e7722..84a2d1f69e 100644
--- a/actionpack/test/dispatch/request_test.rb
+++ b/actionpack/test/dispatch/request_test.rb
@@ -329,20 +329,20 @@ class RequestPort < BaseRequestTest
 
   test "standard_port?" do
     request = stub_request
-    assert !request.ssl?
-    assert request.standard_port?
+    assert_not_predicate request, :ssl?
+    assert_predicate request, :standard_port?
 
     request = stub_request "HTTPS" => "on"
-    assert request.ssl?
-    assert request.standard_port?
+    assert_predicate request, :ssl?
+    assert_predicate request, :standard_port?
 
     request = stub_request "HTTP_HOST" => "www.example.org:8080"
-    assert !request.ssl?
-    assert !request.standard_port?
+    assert_not_predicate request, :ssl?
+    assert_not_predicate request, :standard_port?
 
     request = stub_request "HTTP_HOST" => "www.example.org:8443", "HTTPS" => "on"
-    assert request.ssl?
-    assert !request.standard_port?
+    assert_predicate request, :ssl?
+    assert_not_predicate request, :standard_port?
   end
 
   test "optional port" do
@@ -571,7 +571,7 @@ end
 class LocalhostTest < BaseRequestTest
   test "IPs that match localhost" do
     request = stub_request("REMOTE_IP" => "127.1.1.1", "REMOTE_ADDR" => "127.1.1.1")
-    assert request.local?
+    assert_predicate request, :local?
   end
 end
 
@@ -643,37 +643,37 @@ class RequestProtocol < BaseRequestTest
   test "xml http request" do
     request = stub_request
 
-    assert !request.xml_http_request?
-    assert !request.xhr?
+    assert_not_predicate request, :xml_http_request?
+    assert_not_predicate request, :xhr?
 
     request = stub_request "HTTP_X_REQUESTED_WITH" => "DefinitelyNotAjax1.0"
-    assert !request.xml_http_request?
-    assert !request.xhr?
+    assert_not_predicate request, :xml_http_request?
+    assert_not_predicate request, :xhr?
 
     request = stub_request "HTTP_X_REQUESTED_WITH" => "XMLHttpRequest"
-    assert request.xml_http_request?
-    assert request.xhr?
+    assert_predicate request, :xml_http_request?
+    assert_predicate request, :xhr?
   end
 
   test "reports ssl" do
-    assert !stub_request.ssl?
-    assert stub_request("HTTPS" => "on").ssl?
+    assert_not_predicate stub_request, :ssl?
+    assert_predicate stub_request("HTTPS" => "on"), :ssl?
   end
 
   test "reports ssl when proxied via lighttpd" do
-    assert stub_request("HTTP_X_FORWARDED_PROTO" => "https").ssl?
+    assert_predicate stub_request("HTTP_X_FORWARDED_PROTO" => "https"), :ssl?
   end
 
   test "scheme returns https when proxied" do
     request = stub_request "rack.url_scheme" => "http"
-    assert !request.ssl?
+    assert_not_predicate request, :ssl?
     assert_equal "http", request.scheme
 
     request = stub_request(
       "rack.url_scheme" => "http",
       "HTTP_X_FORWARDED_PROTO" => "https"
     )
-    assert request.ssl?
+    assert_predicate request, :ssl?
     assert_equal "https", request.scheme
   end
 end
@@ -700,7 +700,7 @@ class RequestMethod < BaseRequestTest
 
     assert_equal "GET", request.request_method
     assert_equal "GET", request.env["REQUEST_METHOD"]
-    assert request.get?
+    assert_predicate request, :get?
   end
 
   test "invalid http method raises exception" do
@@ -748,7 +748,7 @@ class RequestMethod < BaseRequestTest
 
     assert_equal "POST", request.method
     assert_equal "PATCH",  request.request_method
-    assert request.patch?
+    assert_predicate request, :patch?
   end
 
   test "post masquerading as put" do
@@ -758,7 +758,7 @@ class RequestMethod < BaseRequestTest
     )
     assert_equal "POST", request.method
     assert_equal "PUT",  request.request_method
-    assert request.put?
+    assert_predicate request, :put?
   end
 
   test "post uneffected by local inflections" do
@@ -772,7 +772,7 @@ class RequestMethod < BaseRequestTest
       request = stub_request "REQUEST_METHOD" => "POST"
       assert_equal :post, ActionDispatch::Request::HTTP_METHOD_LOOKUP["POST"]
       assert_equal :post, request.method_symbol
-      assert request.post?
+      assert_predicate request, :post?
     ensure
       # Reset original acronym set
       ActiveSupport::Inflector.inflections do |inflect|
@@ -809,20 +809,20 @@ class RequestFormat < BaseRequestTest
       "QUERY_STRING" => ""
     )
 
-    assert request.xhr?
+    assert_predicate request, :xhr?
     assert_equal Mime[:js], request.format
   end
 
   test "can override format with parameter negative" do
     request = stub_request("QUERY_STRING" => "format=txt")
 
-    assert !request.format.xml?
+    assert_not_predicate request.format, :xml?
   end
 
   test "can override format with parameter positive" do
     request = stub_request("QUERY_STRING" => "format=xml")
 
-    assert request.format.xml?
+    assert_predicate request.format, :xml?
   end
 
   test "formats text/html with accept header" do
@@ -862,15 +862,15 @@ class RequestFormat < BaseRequestTest
     request = stub_request("QUERY_STRING" => "format=hello")
 
     assert_nil request.format
-    assert_not request.format.html?
-    assert_not request.format.xml?
-    assert_not request.format.json?
+    assert_not_predicate request.format, :html?
+    assert_not_predicate request.format, :xml?
+    assert_not_predicate request.format, :json?
   end
 
   test "format does not throw exceptions when malformed parameters" do
     request = stub_request("QUERY_STRING" => "x[y]=1&x[y][][w]=2")
     assert request.formats
-    assert request.format.html?
+    assert_predicate request.format, :html?
   end
 
   test "formats with xhr request" do
@@ -1234,8 +1234,8 @@ class RequestVariant < BaseRequestTest
   test "setting variant to a symbol" do
     @request.variant = :phone
 
-    assert @request.variant.phone?
-    assert_not @request.variant.tablet?
+    assert_predicate @request.variant, :phone?
+    assert_not_predicate @request.variant, :tablet?
     assert @request.variant.any?(:phone, :tablet)
     assert_not @request.variant.any?(:tablet, :desktop)
   end
@@ -1243,9 +1243,9 @@ class RequestVariant < BaseRequestTest
   test "setting variant to an array of symbols" do
     @request.variant = [:phone, :tablet]
 
-    assert @request.variant.phone?
-    assert @request.variant.tablet?
-    assert_not @request.variant.desktop?
+    assert_predicate @request.variant, :phone?
+    assert_predicate @request.variant, :tablet?
+    assert_not_predicate @request.variant, :desktop?
     assert @request.variant.any?(:tablet, :desktop)
     assert_not @request.variant.any?(:desktop, :watch)
   end
@@ -1253,8 +1253,8 @@ class RequestVariant < BaseRequestTest
   test "clearing variant" do
     @request.variant = nil
 
-    assert @request.variant.empty?
-    assert_not @request.variant.phone?
+    assert_empty @request.variant
+    assert_not_predicate @request.variant, :phone?
     assert_not @request.variant.any?(:phone, :tablet)
   end
 
@@ -1273,13 +1273,13 @@ end
 
 class RequestFormData < BaseRequestTest
   test "media_type is from the FORM_DATA_MEDIA_TYPES array" do
-    assert stub_request("CONTENT_TYPE" => "application/x-www-form-urlencoded").form_data?
-    assert stub_request("CONTENT_TYPE" => "multipart/form-data").form_data?
+    assert_predicate stub_request("CONTENT_TYPE" => "application/x-www-form-urlencoded"), :form_data?
+    assert_predicate stub_request("CONTENT_TYPE" => "multipart/form-data"), :form_data?
   end
 
   test "media_type is not from the FORM_DATA_MEDIA_TYPES array" do
-    assert !stub_request("CONTENT_TYPE" => "application/xml").form_data?
-    assert !stub_request("CONTENT_TYPE" => "multipart/related").form_data?
+    assert_not_predicate stub_request("CONTENT_TYPE" => "application/xml"), :form_data?
+    assert_not_predicate stub_request("CONTENT_TYPE" => "multipart/related"), :form_data?
   end
 
   test "no Content-Type header is provided and the request_method is POST" do
@@ -1287,7 +1287,7 @@ class RequestFormData < BaseRequestTest
 
     assert_equal "", request.media_type
     assert_equal "POST", request.request_method
-    assert !request.form_data?
+    assert_not_predicate request, :form_data?
   end
 end
 
diff --git a/actionpack/test/dispatch/response_test.rb b/actionpack/test/dispatch/response_test.rb
index 0b727dad3d..4c8d528507 100644
--- a/actionpack/test/dispatch/response_test.rb
+++ b/actionpack/test/dispatch/response_test.rb
@@ -15,13 +15,13 @@ class ResponseTest < ActiveSupport::TestCase
       @response.await_commit
     }
     @response.commit!
-    assert @response.committed?
+    assert_predicate @response, :committed?
     assert t.join(0.5)
   end
 
   def test_stream_close
     @response.stream.close
-    assert @response.stream.closed?
+    assert_predicate @response.stream, :closed?
   end
 
   def test_stream_write
@@ -257,9 +257,9 @@ class ResponseTest < ActiveSupport::TestCase
     }
     resp.to_a
 
-    assert resp.etag?
-    assert resp.weak_etag?
-    assert_not resp.strong_etag?
+    assert_predicate resp, :etag?
+    assert_predicate resp, :weak_etag?
+    assert_not_predicate resp, :strong_etag?
     assert_equal('W/"202cb962ac59075b964b07152d234b70"', resp.etag)
     assert_equal({ public: true }, resp.cache_control)
 
@@ -275,9 +275,9 @@ class ResponseTest < ActiveSupport::TestCase
     }
     resp.to_a
 
-    assert resp.etag?
-    assert_not resp.weak_etag?
-    assert resp.strong_etag?
+    assert_predicate resp, :etag?
+    assert_not_predicate resp, :weak_etag?
+    assert_predicate resp, :strong_etag?
     assert_equal('"202cb962ac59075b964b07152d234b70"', resp.etag)
   end
 
@@ -356,7 +356,7 @@ class ResponseTest < ActiveSupport::TestCase
   end
 
   test "respond_to? accepts include_private" do
-    assert_not @response.respond_to?(:method_missing)
+    assert_not_respond_to @response, :method_missing
     assert @response.respond_to?(:method_missing, true)
   end
 
diff --git a/actionpack/test/dispatch/routing_assertions_test.rb b/actionpack/test/dispatch/routing_assertions_test.rb
index a5198f2f13..009b6d9bc3 100644
--- a/actionpack/test/dispatch/routing_assertions_test.rb
+++ b/actionpack/test/dispatch/routing_assertions_test.rb
@@ -52,6 +52,8 @@ class RoutingAssertionsTest < ActionController::TestCase
       end
 
       mount engine => "/shelf"
+
+      get "/shelf/foo", controller: "query_articles", action: "index"
     end
   end
 
@@ -154,6 +156,10 @@ class RoutingAssertionsTest < ActionController::TestCase
     assert_match err.message, "This is a really bad msg"
   end
 
+  def test_assert_recognizes_continue_to_recoginize_after_it_tried_engines
+    assert_recognizes({ controller: "query_articles", action: "index" }, "/shelf/foo")
+  end
+
   def test_assert_routing
     assert_routing("/articles", controller: "articles", action: "index")
   end
diff --git a/actionpack/test/dispatch/routing_test.rb b/actionpack/test/dispatch/routing_test.rb
index 8f4e7c96a9..fe314e26b1 100644
--- a/actionpack/test/dispatch/routing_test.rb
+++ b/actionpack/test/dispatch/routing_test.rb
@@ -3313,7 +3313,7 @@ class TestRoutingMapper < ActionDispatch::IntegrationTest
     end
 
     get "/search"
-    assert !@request.params[:action].frozen?
+    assert_not_predicate @request.params[:action], :frozen?
   end
 
   def test_multiple_positional_args_with_the_same_name
@@ -4267,7 +4267,7 @@ class TestOptimizedNamedRoutes < ActionDispatch::IntegrationTest
   def app; APP end
 
   test "enabled when not mounted and default_url_options is empty" do
-    assert Routes.url_helpers.optimize_routes_generation?
+    assert_predicate Routes.url_helpers, :optimize_routes_generation?
   end
 
   test "named route called as singleton method" do
@@ -4500,7 +4500,7 @@ class TestPortConstraints < ActionDispatch::IntegrationTest
 
       get "/integer", to: ok, constraints: { port: 8080  }
       get "/string",  to: ok, constraints: { port: "8080" }
-      get "/array",   to: ok, constraints: { port: [8080] }
+      get "/array/:idx",   to: ok, constraints: { port: [8080], idx: %w[first last] }
       get "/regexp",  to: ok, constraints: { port: /8080/ }
     end
   end
@@ -4529,7 +4529,10 @@ class TestPortConstraints < ActionDispatch::IntegrationTest
     get "http://www.example.com/array"
     assert_response :not_found
 
-    get "http://www.example.com:8080/array"
+    get "http://www.example.com:8080/array/middle"
+    assert_response :not_found
+
+    get "http://www.example.com:8080/array/first"
     assert_response :success
   end
 
diff --git a/actionpack/test/dispatch/system_testing/driver_test.rb b/actionpack/test/dispatch/system_testing/driver_test.rb
index fcdaf7fb4c..a824ee0c84 100644
--- a/actionpack/test/dispatch/system_testing/driver_test.rb
+++ b/actionpack/test/dispatch/system_testing/driver_test.rb
@@ -12,7 +12,8 @@ class DriverTest < ActiveSupport::TestCase
   test "initializing the driver with a browser" do
     driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :chrome, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
     assert_equal :selenium, driver.instance_variable_get(:@name)
-    assert_equal :chrome, driver.instance_variable_get(:@browser)
+    assert_equal :chrome, driver.instance_variable_get(:@browser).name
+    assert_nil driver.instance_variable_get(:@browser).options
     assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
     assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
   end
@@ -20,7 +21,7 @@ class DriverTest < ActiveSupport::TestCase
   test "initializing the driver with a headless chrome" do
     driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :headless_chrome, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
     assert_equal :selenium, driver.instance_variable_get(:@name)
-    assert_equal :headless_chrome, driver.instance_variable_get(:@browser)
+    assert_equal :headless_chrome, driver.instance_variable_get(:@browser).name
     assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
     assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
   end
@@ -28,7 +29,7 @@ class DriverTest < ActiveSupport::TestCase
   test "initializing the driver with a headless firefox" do
     driver = ActionDispatch::SystemTesting::Driver.new(:selenium, using: :headless_firefox, screen_size: [1400, 1400], options: { url: "http://example.com/wd/hub" })
     assert_equal :selenium, driver.instance_variable_get(:@name)
-    assert_equal :headless_firefox, driver.instance_variable_get(:@browser)
+    assert_equal :headless_firefox, driver.instance_variable_get(:@browser).name
     assert_equal [1400, 1400], driver.instance_variable_get(:@screen_size)
     assert_equal ({ url: "http://example.com/wd/hub" }), driver.instance_variable_get(:@options)
   end
diff --git a/actionpack/test/dispatch/uploaded_file_test.rb b/actionpack/test/dispatch/uploaded_file_test.rb
index 24c7135c7e..5a584b12e5 100644
--- a/actionpack/test/dispatch/uploaded_file_test.rb
+++ b/actionpack/test/dispatch/uploaded_file_test.rb
@@ -100,14 +100,14 @@ module ActionDispatch
     def test_delegate_eof_to_tempfile
       tf = Class.new { def eof?; true end; }
       uf = Http::UploadedFile.new(tempfile: tf.new)
-      assert uf.eof?
+      assert_predicate uf, :eof?
     end
 
     def test_respond_to?
       tf = Class.new { def read; yield end }
       uf = Http::UploadedFile.new(tempfile: tf.new)
-      assert uf.respond_to?(:headers), "responds to headers"
-      assert uf.respond_to?(:read), "responds to read"
+      assert_respond_to uf, :headers
+      assert_respond_to uf, :read
     end
   end
 end
diff --git a/actionpack/test/journey/nodes/symbol_test.rb b/actionpack/test/journey/nodes/symbol_test.rb
index 1e687acef2..b0622ac71a 100644
--- a/actionpack/test/journey/nodes/symbol_test.rb
+++ b/actionpack/test/journey/nodes/symbol_test.rb
@@ -8,10 +8,10 @@ module ActionDispatch
       class TestSymbol < ActiveSupport::TestCase
         def test_default_regexp?
           sym = Symbol.new "foo"
-          assert sym.default_regexp?
+          assert_predicate sym, :default_regexp?
 
           sym.regexp = nil
-          assert_not sym.default_regexp?
+          assert_not_predicate sym, :default_regexp?
         end
       end
     end
diff --git a/actionpack/test/journey/routes_test.rb b/actionpack/test/journey/routes_test.rb
index 81ce07526f..d5c81a8421 100644
--- a/actionpack/test/journey/routes_test.rb
+++ b/actionpack/test/journey/routes_test.rb
@@ -17,11 +17,11 @@ module ActionDispatch
 
       def test_clear
         mapper.get "/foo(/:id)", to: "foo#bar", as: "aaron"
-        assert_not_predicate routes, :empty?
+        assert_not_empty routes
         assert_equal 1, routes.length
 
         routes.clear
-        assert routes.empty?
+        assert_empty routes
         assert_equal 0, routes.length
       end
 
@@ -43,7 +43,7 @@ module ActionDispatch
         mapper.get "/foo(/:id)", to: "foo#bar", as: "aaron"
 
         assert_equal 1, @routes.anchored_routes.length
-        assert_predicate @routes.custom_routes, :empty?
+        assert_empty @routes.custom_routes
 
         mapper.get "/hello/:who", to: "foo#bar", as: "bar", who: /\d/
 
diff --git a/actionpack/test/tmp/.gitignore b/actionpack/test/tmp/.gitignore
deleted file mode 100644
index e69de29bb2..0000000000
--- a/actionpack/test/tmp/.gitignore
+++ /dev/null
diff --git a/actionview/.gitignore b/actionview/.gitignore
index 0a04b29786..246aabbb7f 100644
--- a/actionview/.gitignore
+++ b/actionview/.gitignore
@@ -1,2 +1,5 @@
-/lib/assets/compiled
-/tmp
+/lib/assets/compiled/
+/log/
+/test/fixtures/public/absolute/
+/test/ujs/log/
+/tmp/
diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index c38e11dc38..be0afe4198 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,79 +1,8 @@
-*   Allow the use of callable objects as group methods for grouped selects.
+## Rails 6.0.0.alpha (Unreleased) ##
 
-    Until now, the `option_groups_from_collection_for_select` method was only able to
-    handle method names as `group_method` and `group_label_method` parameters,
-    it is now able to receive procs and other callable objects too.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *Jérémie Bonal*
+    *Jeremy Daer*
 
-*   Add `preload_link_tag` helper
 
-    This helper that allows to the browser to initiate early fetch of resources
-    (different to the specified in `javascript_include_tag` and `stylesheet_link_tag`).
-    Additionally, this sends Early Hints if supported by browser.
-
-    *Guillermo Iguaran*
-
-## Rails 5.2.0.beta2 (November 28, 2017) ##
-
-*   No changes.
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Change `form_with` to generates ids by default.
-
-    When `form_with` was introduced we disabled the automatic generation of ids
-    that was enabled in `form_for`. This usually is not an good idea since labels don't work
-    when the input doesn't have an id and it made harder to test with Capybara.
-
-    You can still disable the automatic generation of ids setting `config.action_view.form_with_generates_ids`
-    to `false.`
-
-    *Nick Pezza*
-
-*   Fix issues with `field_error_proc` wrapping `optgroup` and select divider `option`.
-
-    Fixes #31088
-
-    *Matthias Neumayr*
-
-*   Remove deprecated Erubis ERB handler.
-
-    *Rafael Mendonça França*
-
-*   Remove default `alt` text generation.
-
-    Fixes #30096
-
-    *Cameron Cundiff*
-
-*   Add `srcset` option to `image_tag` helper.
-
-    *Roberto Miranda*
-
-*   Fix issues with scopes and engine on `current_page?` method.
-
-    Fixes #29401.
-
-    *Nikita Savrov*
-
-*   Generate field ids in `collection_check_boxes` and `collection_radio_buttons`.
-
-    This makes sure that the labels are linked up with the fields.
-
-    Fixes #29014.
-
-    *Yuji Yaginuma*
-
-*   Add `:json` type to `auto_discovery_link_tag` to support [JSON Feeds](https://jsonfeed.org/version/1)
-
-    *Mike Gunderloy*
-
-*   Update `distance_of_time_in_words` helper to display better error messages
-    for bad input.
-
-    *Jay Hayes*
-
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/actionview/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/actionview/CHANGELOG.md) for previous changes.
diff --git a/actionview/actionview.gemspec b/actionview/actionview.gemspec
index b99137fcf6..49ee1a292b 100644
--- a/actionview/actionview.gemspec
+++ b/actionview/actionview.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Rendering framework putting the V in MVC (part of Rails)."
   s.description = "Simple, battle-tested conventions and helpers for building web pages."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/actionview/app/assets/javascripts/README.md b/actionview/app/assets/javascripts/README.md
index 8198011b02..185dddc7e5 100644
--- a/actionview/app/assets/javascripts/README.md
+++ b/actionview/app/assets/javascripts/README.md
@@ -50,6 +50,6 @@ Run `bundle exec rake ujs:server` first, and then run the web tests by visiting
 
 rails-ujs is released under the [MIT License](MIT-LICENSE).
 
-[data]: http://www.w3.org/TR/html5/dom.html#embedding-custom-non-visible-data-with-the-data-*-attributes "Embedding custom non-visible data with the data-* attributes"
+[data]: https://www.w3.org/TR/html5/dom.html#embedding-custom-non-visible-data-with-the-data-attributes "Embedding custom non-visible data with the data-* attributes"
 [validator]: http://validator.w3.org/
 [csrf]: http://api.rubyonrails.org/classes/ActionController/RequestForgeryProtection.html
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
index cc0e037428..2a8f5659e3 100644
--- a/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/ajax.coffee
@@ -1,7 +1,8 @@
+#= require ./csp
 #= require ./csrf
 #= require ./event
 
-{ CSRFProtection, fire } = Rails
+{ cspNonce, CSRFProtection, fire } = Rails
 
 AcceptHeaders =
   '*': '*/*'
@@ -65,6 +66,7 @@ processResponse = (response, type) ->
       try response = JSON.parse(response)
     else if type.match(/\b(?:java|ecma)script\b/)
       script = document.createElement('script')
+      script.nonce = cspNonce()
       script.text = response
       document.head.appendChild(script).parentNode.removeChild(script)
     else if type.match(/\b(xml|html|svg)\b/)
diff --git a/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee b/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee
new file mode 100644
index 0000000000..8d2d6ce447
--- /dev/null
+++ b/actionview/app/assets/javascripts/rails-ujs/utils/csp.coffee
@@ -0,0 +1,4 @@
+# Content-Security-Policy nonce for inline scripts
+cspNonce = Rails.cspNonce = ->
+  meta = document.querySelector('meta[name=csp-nonce]')
+  meta and meta.content
diff --git a/actionview/lib/action_view/gem_version.rb b/actionview/lib/action_view/gem_version.rb
index ff7f2bb853..77ae444a58 100644
--- a/actionview/lib/action_view/gem_version.rb
+++ b/actionview/lib/action_view/gem_version.rb
@@ -7,10 +7,10 @@ module ActionView
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/actionview/lib/action_view/helpers.rb b/actionview/lib/action_view/helpers.rb
index 46f20c4277..8cc8013718 100644
--- a/actionview/lib/action_view/helpers.rb
+++ b/actionview/lib/action_view/helpers.rb
@@ -13,6 +13,7 @@ module ActionView #:nodoc:
     autoload :CacheHelper
     autoload :CaptureHelper
     autoload :ControllerHelper
+    autoload :CspHelper
     autoload :CsrfHelper
     autoload :DateHelper
     autoload :DebugHelper
@@ -46,6 +47,7 @@ module ActionView #:nodoc:
     include CacheHelper
     include CaptureHelper
     include ControllerHelper
+    include CspHelper
     include CsrfHelper
     include DateHelper
     include DebugHelper
diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index 16def9837e..76b1c3fb6e 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -133,7 +133,7 @@ module ActionView
 
         sources_tags = sources.uniq.map { |source|
           href = path_to_stylesheet(source, path_options)
-          early_hints_links << "<#{href}>; rel=preload; as=stylesheet"
+          early_hints_links << "<#{href}>; rel=preload; as=style"
           tag_options = {
             "rel" => "stylesheet",
             "media" => "screen",
diff --git a/actionview/lib/action_view/helpers/csp_helper.rb b/actionview/lib/action_view/helpers/csp_helper.rb
new file mode 100644
index 0000000000..e2e065c218
--- /dev/null
+++ b/actionview/lib/action_view/helpers/csp_helper.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module ActionView
+  # = Action View CSP Helper
+  module Helpers #:nodoc:
+    module CspHelper
+      # Returns a meta tag "csp-nonce" with the per-session nonce value
+      # for allowing inline <script> tags.
+      #
+      #   <head>
+      #     <%= csp_meta_tag %>
+      #   </head>
+      #
+      # This is used by the Rails UJS helper to create dynamically
+      # loaded inline <script> elements.
+      #
+      def csp_meta_tag
+        if content_security_policy?
+          tag("meta", name: "csp-nonce", content: content_security_policy_nonce)
+        end
+      end
+    end
+  end
+end
diff --git a/actionview/lib/action_view/helpers/date_helper.rb b/actionview/lib/action_view/helpers/date_helper.rb
index 09040ccbc4..4c45f122fe 100644
--- a/actionview/lib/action_view/helpers/date_helper.rb
+++ b/actionview/lib/action_view/helpers/date_helper.rb
@@ -116,7 +116,7 @@ module ActionView
             when 10..19 then locale.t :less_than_x_seconds, count: 20
             when 20..39 then locale.t :half_a_minute
             when 40..59 then locale.t :less_than_x_minutes, count: 1
-              else             locale.t :x_minutes,           count: 1
+            else             locale.t :x_minutes,           count: 1
             end
 
           when 2...45           then locale.t :x_minutes,      count: distance_in_minutes
@@ -131,7 +131,7 @@ module ActionView
           when 43200...86400    then locale.t :about_x_months, count: (distance_in_minutes.to_f / 43200.0).round
             # 60 days up to 365 days
           when 86400...525600   then locale.t :x_months,       count: (distance_in_minutes.to_f / 43200.0).round
-            else
+          else
             from_year = from_time.year
             from_year += 1 if from_time.month >= 3
             to_year = to_time.year
diff --git a/actionview/lib/action_view/helpers/debug_helper.rb b/actionview/lib/action_view/helpers/debug_helper.rb
index 52dff1f750..88ceba414b 100644
--- a/actionview/lib/action_view/helpers/debug_helper.rb
+++ b/actionview/lib/action_view/helpers/debug_helper.rb
@@ -24,7 +24,7 @@ module ActionView
       #     created_at:
       #   </pre>
       def debug(object)
-        Marshal::dump(object)
+        Marshal.dump(object)
         object = ERB::Util.html_escape(object.to_yaml)
         content_tag(:pre, object, class: "debug_dump")
       rescue # errors from Marshal or YAML
diff --git a/actionview/lib/action_view/helpers/form_helper.rb b/actionview/lib/action_view/helpers/form_helper.rb
index 1df1694325..15aa9ec2dd 100644
--- a/actionview/lib/action_view/helpers/form_helper.rb
+++ b/actionview/lib/action_view/helpers/form_helper.rb
@@ -1014,14 +1014,13 @@ module ActionView
       #   <%= fields :comment do |fields| %>
       #     <%= fields.text_field :body %>
       #   <% end %>
-      #   # => <input type="text" name="comment[body]>
+      #   # => <input type="text" name="comment[body]">
       #
       #   # Using a model infers the scope and assigns field values:
-      #   <%= fields model: Comment.new(body: "full bodied") do |fields| %<
+      #   <%= fields model: Comment.new(body: "full bodied") do |fields| %>
       #     <%= fields.text_field :body %>
       #   <% end %>
-      #   # =>
-      #   <input type="text" name="comment[body] value="full bodied">
+      #   # => <input type="text" name="comment[body]" value="full bodied">
       #
       #   # Using +fields+ with +form_with+:
       #   <%= form_with model: @post do |form| %>
diff --git a/actionview/lib/action_view/helpers/javascript_helper.rb b/actionview/lib/action_view/helpers/javascript_helper.rb
index dd2cd57ac3..acc50f8a62 100644
--- a/actionview/lib/action_view/helpers/javascript_helper.rb
+++ b/actionview/lib/action_view/helpers/javascript_helper.rb
@@ -63,6 +63,13 @@ module ActionView
       #   <%= javascript_tag defer: 'defer' do -%>
       #     alert('All is good')
       #   <% end -%>
+      #
+      # If you have a content security policy enabled then you can add an automatic
+      # nonce value by passing +nonce: true+ as part of +html_options+. Example:
+      #
+      #   <%= javascript_tag nonce: true do -%>
+      #     alert('All is good')
+      #   <% end -%>
       def javascript_tag(content_or_options_with_block = nil, html_options = {}, &block)
         content =
           if block_given?
@@ -72,6 +79,10 @@ module ActionView
             content_or_options_with_block
           end
 
+        if html_options[:nonce] == true
+          html_options[:nonce] = content_security_policy_nonce
+        end
+
         content_tag("script".freeze, javascript_cdata_section(content), html_options)
       end
 
diff --git a/actionview/lib/action_view/helpers/tags/translator.rb b/actionview/lib/action_view/helpers/tags/translator.rb
index fcf96d2c9c..e81ca3aef0 100644
--- a/actionview/lib/action_view/helpers/tags/translator.rb
+++ b/actionview/lib/action_view/helpers/tags/translator.rb
@@ -16,13 +16,8 @@ module ActionView
           translated_attribute || human_attribute_name
         end
 
-        # TODO Change this to private once we've dropped Ruby 2.2 support.
-        # Workaround for Ruby 2.2 "private attribute?" warning.
-        protected
-
-          attr_reader :object_name, :method_and_value, :scope, :model
-
         private
+          attr_reader :object_name, :method_and_value, :scope, :model
 
           def i18n_default
             if model
diff --git a/actionview/lib/action_view/helpers/text_helper.rb b/actionview/lib/action_view/helpers/text_helper.rb
index 84d38aa416..34138de00e 100644
--- a/actionview/lib/action_view/helpers/text_helper.rb
+++ b/actionview/lib/action_view/helpers/text_helper.rb
@@ -13,9 +13,9 @@ module ActionView
     #
     # ==== Sanitization
     #
-    # Most text helpers by default sanitize the given content, but do not escape it.
-    # This means HTML tags will appear in the page but all malicious code will be removed.
-    # Let's look at some examples using the +simple_format+ method:
+    # Most text helpers that generate HTML output sanitize the given input by default,
+    # but do not escape it. This means HTML tags will appear in the page but all malicious
+    # code will be removed. Let's look at some examples using the +simple_format+ method:
     #
     #   simple_format('<a href="http://example.com/">Example</a>')
     #   # => "<p><a href=\"http://example.com/\">Example</a></p>"
@@ -128,7 +128,7 @@ module ActionView
       #   # => You searched for: <a href="search?q=rails">rails</a>
       #
       #   highlight('<a href="javascript:alert(\'no!\')">ruby</a> on rails', 'rails', sanitize: false)
-      #   # => "<a>ruby</a> on <mark>rails</mark>"
+      #   # => <a href="javascript:alert('no!')">ruby</a> on <mark>rails</mark>
       def highlight(text, phrases, options = {})
         text = sanitize(text) if options.fetch(:sanitize, true)
 
diff --git a/actionview/package.json b/actionview/package.json
index 787ae06208..624eb5de93 100644
--- a/actionview/package.json
+++ b/actionview/package.json
@@ -1,6 +1,6 @@
 {
   "name": "rails-ujs",
-  "version": "5.2.0-beta2",
+  "version": "6.0.0-alpha",
   "description": "Ruby on Rails unobtrusive scripting adapter",
   "main": "lib/assets/compiled/rails-ujs.js",
   "files": [
diff --git a/actionview/test/fixtures/public/.gitignore b/actionview/test/fixtures/public/.gitignore
deleted file mode 100644
index 312e635ee6..0000000000
--- a/actionview/test/fixtures/public/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-absolute/*
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 284dacf2d4..6d98eacfb8 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -407,7 +407,7 @@ class AssetTagHelperTest < ActionView::TestCase
   end
 
   def test_javascript_include_tag_is_html_safe
-    assert javascript_include_tag("prototype").html_safe?
+    assert_predicate javascript_include_tag("prototype"), :html_safe?
   end
 
   def test_javascript_include_tag_relative_protocol
@@ -460,8 +460,8 @@ class AssetTagHelperTest < ActionView::TestCase
   end
 
   def test_stylesheet_link_tag_is_html_safe
-    assert stylesheet_link_tag("dir/file").html_safe?
-    assert stylesheet_link_tag("dir/other/file", "dir/file2").html_safe?
+    assert_predicate stylesheet_link_tag("dir/file"), :html_safe?
+    assert_predicate stylesheet_link_tag("dir/other/file", "dir/file2"), :html_safe?
   end
 
   def test_stylesheet_link_tag_escapes_options
diff --git a/actionview/test/template/atom_feed_helper_test.rb b/actionview/test/template/atom_feed_helper_test.rb
index 1be20dcaae..8e683cb48a 100644
--- a/actionview/test/template/atom_feed_helper_test.rb
+++ b/actionview/test/template/atom_feed_helper_test.rb
@@ -257,7 +257,7 @@ class AtomFeedTest < ActionController::TestCase
       get :index, params: { id: "provide_builder" }
       # because we pass in the non-default builder, the content generated by the
       # helper should go 'nowhere'.  Leaving the response body blank.
-      assert @response.body.blank?
+      assert_predicate @response.body, :blank?
     end
   end
 
diff --git a/actionview/test/template/capture_helper_test.rb b/actionview/test/template/capture_helper_test.rb
index 8a1c00fd00..31c280a91c 100644
--- a/actionview/test/template/capture_helper_test.rb
+++ b/actionview/test/template/capture_helper_test.rb
@@ -155,12 +155,12 @@ class CaptureHelperTest < ActionView::TestCase
     content_for :title do
       content_tag(:p, "title")
     end
-    assert content_for(:title).html_safe?
+    assert_predicate content_for(:title), :html_safe?
     content_for :title, "", flush: true
     content_for(:title) do
       content_tag(:p, "title")
     end
-    assert content_for(:title).html_safe?
+    assert_predicate content_for(:title), :html_safe?
   end
 
   def test_provide
diff --git a/actionview/test/template/date_helper_test.rb b/actionview/test/template/date_helper_test.rb
index 97cfd754be..94357d5f90 100644
--- a/actionview/test/template/date_helper_test.rb
+++ b/actionview/test/template/date_helper_test.rb
@@ -144,15 +144,13 @@ class DateHelperTest < ActionView::TestCase
     rubinius_skip "Date is written in Ruby and relies on Fixnum#/"
     jruby_skip "Date is written in Ruby and relies on Fixnum#/"
 
-    klass = RUBY_VERSION > "2.4" ? Integer : Fixnum
-
     # Make sure that we avoid {Integer,Fixnum}#/ (redefined by mathn)
-    klass.send :private, :/
+    Integer.send :private, :/
 
     from = Time.utc(2004, 6, 6, 21, 45, 0)
     assert_distance_of_time_in_words(from)
   ensure
-    klass.send :public, :/
+    Integer.send :public, :/
   end
 
   def test_time_ago_in_words_passes_include_seconds
@@ -3593,25 +3591,25 @@ class DateHelperTest < ActionView::TestCase
   end
 
   def test_select_html_safety
-    assert select_day(16).html_safe?
-    assert select_month(8).html_safe?
-    assert select_year(Time.mktime(2003, 8, 16, 8, 4, 18)).html_safe?
-    assert select_minute(Time.mktime(2003, 8, 16, 8, 4, 18)).html_safe?
-    assert select_second(Time.mktime(2003, 8, 16, 8, 4, 18)).html_safe?
+    assert_predicate select_day(16), :html_safe?
+    assert_predicate select_month(8), :html_safe?
+    assert_predicate select_year(Time.mktime(2003, 8, 16, 8, 4, 18)), :html_safe?
+    assert_predicate select_minute(Time.mktime(2003, 8, 16, 8, 4, 18)), :html_safe?
+    assert_predicate select_second(Time.mktime(2003, 8, 16, 8, 4, 18)), :html_safe?
 
-    assert select_minute(8, use_hidden: true).html_safe?
-    assert select_month(8, prompt: "Choose month").html_safe?
+    assert_predicate select_minute(8, use_hidden: true), :html_safe?
+    assert_predicate select_month(8, prompt: "Choose month"), :html_safe?
 
-    assert select_time(Time.mktime(2003, 8, 16, 8, 4, 18), {}, { class: "selector" }).html_safe?
-    assert select_date(Time.mktime(2003, 8, 16), date_separator: " / ", start_year: 2003, end_year: 2005, prefix: "date[first]").html_safe?
+    assert_predicate select_time(Time.mktime(2003, 8, 16, 8, 4, 18), {}, { class: "selector" }), :html_safe?
+    assert_predicate select_date(Time.mktime(2003, 8, 16), date_separator: " / ", start_year: 2003, end_year: 2005, prefix: "date[first]"), :html_safe?
   end
 
   def test_object_select_html_safety
     @post = Post.new
     @post.written_on = Date.new(2004, 6, 15)
 
-    assert date_select("post", "written_on", default: Time.local(2006, 9, 19, 15, 16, 35), include_blank: true).html_safe?
-    assert time_select("post", "written_on", ignore_date: true).html_safe?
+    assert_predicate date_select("post", "written_on", default: Time.local(2006, 9, 19, 15, 16, 35), include_blank: true), :html_safe?
+    assert_predicate time_select("post", "written_on", ignore_date: true), :html_safe?
   end
 
   def test_time_tag_with_date
diff --git a/actionview/test/template/erb_util_test.rb b/actionview/test/template/erb_util_test.rb
index 8b804105f4..bd702dbe94 100644
--- a/actionview/test/template/erb_util_test.rb
+++ b/actionview/test/template/erb_util_test.rb
@@ -70,24 +70,24 @@ class ErbUtilTest < ActiveSupport::TestCase
 
   def test_json_escape_returns_unsafe_strings_when_passed_unsafe_strings
     value = json_escape("asdf")
-    assert !value.html_safe?
+    assert_not_predicate value, :html_safe?
   end
 
   def test_json_escape_returns_safe_strings_when_passed_safe_strings
     value = json_escape("asdf".html_safe)
-    assert value.html_safe?
+    assert_predicate value, :html_safe?
   end
 
   def test_html_escape_is_html_safe
     escaped = h("<p>")
     assert_equal "&lt;p&gt;", escaped
-    assert escaped.html_safe?
+    assert_predicate escaped, :html_safe?
   end
 
   def test_html_escape_passes_html_escape_unmodified
     escaped = h("<p>".html_safe)
     assert_equal "<p>", escaped
-    assert escaped.html_safe?
+    assert_predicate escaped, :html_safe?
   end
 
   def test_rest_in_ascii
@@ -104,11 +104,11 @@ class ErbUtilTest < ActiveSupport::TestCase
 
   def test_html_escape_once_returns_unsafe_strings_when_passed_unsafe_strings
     value = html_escape_once("1 < 2 &amp; 3")
-    assert !value.html_safe?
+    assert_not_predicate value, :html_safe?
   end
 
   def test_html_escape_once_returns_safe_strings_when_passed_safe_strings
     value = html_escape_once("1 < 2 &amp; 3".html_safe)
-    assert value.html_safe?
+    assert_predicate value, :html_safe?
   end
 end
diff --git a/actionview/test/template/form_helper/form_with_test.rb b/actionview/test/template/form_helper/form_with_test.rb
index 0295ff627d..0d224d0c46 100644
--- a/actionview/test/template/form_helper/form_with_test.rb
+++ b/actionview/test/template/form_helper/form_with_test.rb
@@ -108,7 +108,7 @@ class FormWithActsLikeFormTagTest < FormWithTest
     actual = form_with(skip_enforcing_utf8: true)
     expected = whole_form("http://www.example.com", skip_enforcing_utf8: true)
     assert_dom_equal expected, actual
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
   end
 
   def test_form_with_with_block_in_erb
diff --git a/actionview/test/template/form_helper_test.rb b/actionview/test/template/form_helper_test.rb
index 6a317e1a12..b8fad090c5 100644
--- a/actionview/test/template/form_helper_test.rb
+++ b/actionview/test/template/form_helper_test.rb
@@ -612,7 +612,7 @@ class FormHelperTest < ActionView::TestCase
   end
 
   def test_check_box_is_html_safe
-    assert check_box("post", "secret").html_safe?
+    assert_predicate check_box("post", "secret"), :html_safe?
   end
 
   def test_check_box_checked_if_object_value_is_same_that_check_value
@@ -775,7 +775,7 @@ class FormHelperTest < ActionView::TestCase
   end
 
   def test_check_box_with_nil_unchecked_value_is_html_safe
-    assert check_box("post", "secret", {}, "on", nil).html_safe?
+    assert_predicate check_box("post", "secret", {}, "on", nil), :html_safe?
   end
 
   def test_check_box_with_multiple_behavior
diff --git a/actionview/test/template/form_options_helper_test.rb b/actionview/test/template/form_options_helper_test.rb
index 642f450f91..f82eada869 100644
--- a/actionview/test/template/form_options_helper_test.rb
+++ b/actionview/test/template/form_options_helper_test.rb
@@ -354,7 +354,7 @@ class FormOptionsHelperTest < ActionView::TestCase
   end
 
   def test_option_groups_from_collection_for_select_returns_html_safe_string
-    assert option_groups_from_collection_for_select(dummy_continents, "countries", "continent_name", "country_id", "country_name", "dk").html_safe?
+    assert_predicate option_groups_from_collection_for_select(dummy_continents, "countries", "continent_name", "country_id", "country_name", "dk"), :html_safe?
   end
 
   def test_grouped_options_for_select_with_array
@@ -402,7 +402,7 @@ class FormOptionsHelperTest < ActionView::TestCase
   end
 
   def test_grouped_options_for_select_returns_html_safe_string
-    assert grouped_options_for_select([["Hats", ["Baseball Cap", "Cowboy Hat"]]]).html_safe?
+    assert_predicate grouped_options_for_select([["Hats", ["Baseball Cap", "Cowboy Hat"]]]), :html_safe?
   end
 
   def test_grouped_options_for_select_with_prompt_returns_html_escaped_string
@@ -492,7 +492,7 @@ class FormOptionsHelperTest < ActionView::TestCase
   end
 
   def test_time_zone_options_returns_html_safe_string
-    assert time_zone_options_for_select.html_safe?
+    assert_predicate time_zone_options_for_select, :html_safe?
   end
 
   def test_select
diff --git a/actionview/test/template/form_tag_helper_test.rb b/actionview/test/template/form_tag_helper_test.rb
index 5e328ebf53..0d9bf77f98 100644
--- a/actionview/test/template/form_tag_helper_test.rb
+++ b/actionview/test/template/form_tag_helper_test.rb
@@ -142,14 +142,14 @@ class FormTagHelperTest < ActionView::TestCase
     actual = form_tag({}, { enforce_utf8: true })
     expected = whole_form("http://www.example.com", enforce_utf8: true)
     assert_dom_equal expected, actual
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
   end
 
   def test_form_tag_enforce_utf8_false
     actual = form_tag({}, { enforce_utf8: false })
     expected = whole_form("http://www.example.com", enforce_utf8: false)
     assert_dom_equal expected, actual
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
   end
 
   def test_form_tag_with_block_in_erb
diff --git a/actionview/test/template/lookup_context_test.rb b/actionview/test/template/lookup_context_test.rb
index 402ee9b6ae..beee76f711 100644
--- a/actionview/test/template/lookup_context_test.rb
+++ b/actionview/test/template/lookup_context_test.rb
@@ -35,7 +35,7 @@ class LookupContextTest < ActiveSupport::TestCase
 
   test "allows me to freeze and retrieve frozen formats" do
     @lookup_context.formats.freeze
-    assert @lookup_context.formats.frozen?
+    assert_predicate @lookup_context.formats, :frozen?
   end
 
   test "provides getters and setters for variants" do
diff --git a/actionview/test/template/number_helper_test.rb b/actionview/test/template/number_helper_test.rb
index e92bf66203..357ae1326a 100644
--- a/actionview/test/template/number_helper_test.rb
+++ b/actionview/test/template/number_helper_test.rb
@@ -126,43 +126,43 @@ class NumberHelperTest < ActionView::TestCase
   end
 
   def test_number_helpers_outputs_are_html_safe
-    assert number_to_human(1).html_safe?
-    assert !number_to_human("<script></script>").html_safe?
-    assert number_to_human("asdf".html_safe).html_safe?
-    assert number_to_human("1".html_safe).html_safe?
-
-    assert number_to_human_size(1).html_safe?
-    assert number_to_human_size(1000000).html_safe?
-    assert !number_to_human_size("<script></script>").html_safe?
-    assert number_to_human_size("asdf".html_safe).html_safe?
-    assert number_to_human_size("1".html_safe).html_safe?
-
-    assert number_with_precision(1, strip_insignificant_zeros: false).html_safe?
-    assert number_with_precision(1, strip_insignificant_zeros: true).html_safe?
-    assert !number_with_precision("<script></script>").html_safe?
-    assert number_with_precision("asdf".html_safe).html_safe?
-    assert number_with_precision("1".html_safe).html_safe?
-
-    assert number_to_currency(1).html_safe?
-    assert !number_to_currency("<script></script>").html_safe?
-    assert number_to_currency("asdf".html_safe).html_safe?
-    assert number_to_currency("1".html_safe).html_safe?
-
-    assert number_to_percentage(1).html_safe?
-    assert !number_to_percentage("<script></script>").html_safe?
-    assert number_to_percentage("asdf".html_safe).html_safe?
-    assert number_to_percentage("1".html_safe).html_safe?
-
-    assert number_to_phone(1).html_safe?
+    assert_predicate number_to_human(1), :html_safe?
+    assert_not_predicate number_to_human("<script></script>"), :html_safe?
+    assert_predicate number_to_human("asdf".html_safe), :html_safe?
+    assert_predicate number_to_human("1".html_safe), :html_safe?
+
+    assert_predicate number_to_human_size(1), :html_safe?
+    assert_predicate number_to_human_size(1000000), :html_safe?
+    assert_not_predicate number_to_human_size("<script></script>"), :html_safe?
+    assert_predicate number_to_human_size("asdf".html_safe), :html_safe?
+    assert_predicate number_to_human_size("1".html_safe), :html_safe?
+
+    assert_predicate number_with_precision(1, strip_insignificant_zeros: false), :html_safe?
+    assert_predicate number_with_precision(1, strip_insignificant_zeros: true), :html_safe?
+    assert_not_predicate number_with_precision("<script></script>"), :html_safe?
+    assert_predicate number_with_precision("asdf".html_safe), :html_safe?
+    assert_predicate number_with_precision("1".html_safe), :html_safe?
+
+    assert_predicate number_to_currency(1), :html_safe?
+    assert_not_predicate number_to_currency("<script></script>"), :html_safe?
+    assert_predicate number_to_currency("asdf".html_safe), :html_safe?
+    assert_predicate number_to_currency("1".html_safe), :html_safe?
+
+    assert_predicate number_to_percentage(1), :html_safe?
+    assert_not_predicate number_to_percentage("<script></script>"), :html_safe?
+    assert_predicate number_to_percentage("asdf".html_safe), :html_safe?
+    assert_predicate number_to_percentage("1".html_safe), :html_safe?
+
+    assert_predicate number_to_phone(1), :html_safe?
     assert_equal "&lt;script&gt;&lt;/script&gt;", number_to_phone("<script></script>")
-    assert number_to_phone("<script></script>").html_safe?
-    assert number_to_phone("asdf".html_safe).html_safe?
-    assert number_to_phone("1".html_safe).html_safe?
-
-    assert number_with_delimiter(1).html_safe?
-    assert !number_with_delimiter("<script></script>").html_safe?
-    assert number_with_delimiter("asdf".html_safe).html_safe?
-    assert number_with_delimiter("1".html_safe).html_safe?
+    assert_predicate number_to_phone("<script></script>"), :html_safe?
+    assert_predicate number_to_phone("asdf".html_safe), :html_safe?
+    assert_predicate number_to_phone("1".html_safe), :html_safe?
+
+    assert_predicate number_with_delimiter(1), :html_safe?
+    assert_not_predicate number_with_delimiter("<script></script>"), :html_safe?
+    assert_predicate number_with_delimiter("asdf".html_safe), :html_safe?
+    assert_predicate number_with_delimiter("1".html_safe), :html_safe?
   end
 
   def test_number_helpers_should_raise_error_if_invalid_when_specified
diff --git a/actionview/test/template/output_safety_helper_test.rb b/actionview/test/template/output_safety_helper_test.rb
index b5e9a77105..faeeded1c8 100644
--- a/actionview/test/template/output_safety_helper_test.rb
+++ b/actionview/test/template/output_safety_helper_test.rb
@@ -12,7 +12,7 @@ class OutputSafetyHelperTest < ActionView::TestCase
   test "raw returns the safe string" do
     result = raw(@string)
     assert_equal @string, result
-    assert result.html_safe?
+    assert_predicate result, :html_safe?
   end
 
   test "raw handles nil values correctly" do
@@ -53,11 +53,11 @@ class OutputSafetyHelperTest < ActionView::TestCase
 
   test "to_sentence should escape non-html_safe values" do
     actual = to_sentence(%w(< > & ' "))
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal("&lt;, &gt;, &amp;, &#39;, and &quot;", actual)
 
     actual = to_sentence(%w(<script>))
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal("&lt;script&gt;", actual)
   end
 
@@ -80,19 +80,19 @@ class OutputSafetyHelperTest < ActionView::TestCase
     url = "https://example.com"
     expected = %(<a href="#{url}">#{url}</a> and <p>&lt;marquee&gt;shady stuff&lt;/marquee&gt;<br /></p>)
     actual = to_sentence([link_to(url, url), ptag])
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal(expected, actual)
   end
 
   test "to_sentence handles blank strings" do
     actual = to_sentence(["", "two", "three"])
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal ", two, and three", actual
   end
 
   test "to_sentence handles nil values" do
     actual = to_sentence([nil, "two", "three"])
-    assert actual.html_safe?
+    assert_predicate actual, :html_safe?
     assert_equal ", two, and three", actual
   end
 
diff --git a/actionview/test/template/sanitize_helper_test.rb b/actionview/test/template/sanitize_helper_test.rb
index 0e690c82cb..181f09ab65 100644
--- a/actionview/test/template/sanitize_helper_test.rb
+++ b/actionview/test/template/sanitize_helper_test.rb
@@ -38,6 +38,6 @@ class SanitizeHelperTest < ActionView::TestCase
   end
 
   def test_sanitize_is_marked_safe
-    assert sanitize("<html><script></script></html>").html_safe?
+    assert_predicate sanitize("<html><script></script></html>"), :html_safe?
   end
 end
diff --git a/actionview/test/template/tag_helper_test.rb b/actionview/test/template/tag_helper_test.rb
index a746b9c1b5..9a6226fd04 100644
--- a/actionview/test/template/tag_helper_test.rb
+++ b/actionview/test/template/tag_helper_test.rb
@@ -81,7 +81,7 @@ class TagHelperTest < ActionView::TestCase
 
   def test_content_tag
     assert_equal "<a href=\"create\">Create</a>", content_tag("a", "Create", "href" => "create")
-    assert content_tag("a", "Create", "href" => "create").html_safe?
+    assert_predicate content_tag("a", "Create", "href" => "create"), :html_safe?
     assert_equal content_tag("a", "Create", "href" => "create"),
                  content_tag("a", "Create", href: "create")
     assert_equal "<p>&lt;script&gt;evil_js&lt;/script&gt;</p>",
@@ -92,7 +92,7 @@ class TagHelperTest < ActionView::TestCase
 
   def test_tag_builder_with_content
     assert_equal "<div id=\"post_1\">Content</div>", tag.div("Content", id: "post_1")
-    assert tag.div("Content", id: "post_1").html_safe?
+    assert_predicate tag.div("Content", id: "post_1"), :html_safe?
     assert_equal tag.div("Content", id: "post_1"),
                  tag.div("Content", "id": "post_1")
     assert_equal "<p>&lt;script&gt;evil_js&lt;/script&gt;</p>",
diff --git a/actionview/test/template/text_helper_test.rb b/actionview/test/template/text_helper_test.rb
index f247de066f..45edfe18be 100644
--- a/actionview/test/template/text_helper_test.rb
+++ b/actionview/test/template/text_helper_test.rb
@@ -19,12 +19,12 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_simple_format_should_be_html_safe
-    assert simple_format("<b> test with html tags </b>").html_safe?
+    assert_predicate simple_format("<b> test with html tags </b>"), :html_safe?
   end
 
   def test_simple_format_included_in_isolation
     helper_klass = Class.new { include ActionView::Helpers::TextHelper }
-    assert helper_klass.new.simple_format("<b> test with html tags </b>").html_safe?
+    assert_predicate helper_klass.new.simple_format("<b> test with html tags </b>"), :html_safe?
   end
 
   def test_simple_format
@@ -123,7 +123,7 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_truncate_should_be_html_safe
-    assert truncate("Hello World!", length: 12).html_safe?
+    assert_predicate truncate("Hello World!", length: 12), :html_safe?
   end
 
   def test_truncate_should_escape_the_input
@@ -136,12 +136,12 @@ class TextHelperTest < ActionView::TestCase
 
   def test_truncate_with_escape_false_should_be_html_safe
     truncated = truncate("Hello <script>code!</script>World!!", length: 12, escape: false)
-    assert truncated.html_safe?
+    assert_predicate truncated, :html_safe?
   end
 
   def test_truncate_with_block_should_be_html_safe
     truncated = truncate("Here's a long test and I need a continue to read link", length: 27) { link_to "Continue", "#" }
-    assert truncated.html_safe?
+    assert_predicate truncated, :html_safe?
   end
 
   def test_truncate_with_block_should_escape_the_input
@@ -156,7 +156,7 @@ class TextHelperTest < ActionView::TestCase
 
   def test_truncate_with_block_with_escape_false_should_be_html_safe
     truncated = truncate("<script>code!</script>Here's a long test and I need a continue to read link", length: 27, escape: false) { link_to "Continue", "#" }
-    assert truncated.html_safe?
+    assert_predicate truncated, :html_safe?
   end
 
   def test_truncate_with_block_should_escape_the_block
@@ -165,7 +165,7 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_highlight_should_be_html_safe
-    assert highlight("This is a beautiful morning", "beautiful").html_safe?
+    assert_predicate highlight("This is a beautiful morning", "beautiful"), :html_safe?
   end
 
   def test_highlight
@@ -297,7 +297,7 @@ class TextHelperTest < ActionView::TestCase
   end
 
   def test_excerpt_should_not_be_html_safe
-    assert !excerpt("This is a beautiful! morning", "beautiful", radius: 5).html_safe?
+    assert_not_predicate excerpt("This is a beautiful! morning", "beautiful", radius: 5), :html_safe?
   end
 
   def test_excerpt_in_borderline_cases
diff --git a/actionview/test/template/translation_helper_test.rb b/actionview/test/template/translation_helper_test.rb
index 8956a584ff..f40595bf4d 100644
--- a/actionview/test/template/translation_helper_test.rb
+++ b/actionview/test/template/translation_helper_test.rb
@@ -75,7 +75,7 @@ class TranslationHelperTest < ActiveSupport::TestCase
   def test_returns_missing_translation_message_with_unescaped_interpolation
     expected = '<span class="translation_missing" title="translation missing: en.translations.missing, name: Kir, year: 2015, vulnerable: &amp;quot; onclick=&amp;quot;alert()&amp;quot;">Missing</span>'
     assert_equal expected, translate(:"translations.missing", name: "Kir", year: "2015", vulnerable: %{" onclick="alert()"})
-    assert translate(:"translations.missing").html_safe?
+    assert_predicate translate(:"translations.missing"), :html_safe?
   end
 
   def test_returns_missing_translation_message_does_filters_out_i18n_options
@@ -145,11 +145,11 @@ class TranslationHelperTest < ActiveSupport::TestCase
   end
 
   def test_translate_marks_translations_named_html_as_safe_html
-    assert translate(:'translations.html').html_safe?
+    assert_predicate translate(:'translations.html'), :html_safe?
   end
 
   def test_translate_marks_translations_with_a_html_suffix_as_safe_html
-    assert translate(:'translations.hello_html').html_safe?
+    assert_predicate translate(:'translations.hello_html'), :html_safe?
   end
 
   def test_translate_escapes_interpolations_in_translations_with_a_html_suffix
diff --git a/actionview/test/template/url_helper_test.rb b/actionview/test/template/url_helper_test.rb
index 0cd0386cac..8bccda481b 100644
--- a/actionview/test/template/url_helper_test.rb
+++ b/actionview/test/template/url_helper_test.rb
@@ -663,7 +663,7 @@ class UrlHelperTest < ActiveSupport::TestCase
   end
 
   def test_mail_to_returns_html_safe_string
-    assert mail_to("david@loudthinking.com").html_safe?
+    assert_predicate mail_to("david@loudthinking.com"), :html_safe?
   end
 
   def test_mail_to_with_block
diff --git a/actionview/test/tmp/.keep b/actionview/test/tmp/.keep
deleted file mode 100644
index e69de29bb2..0000000000
--- a/actionview/test/tmp/.keep
+++ /dev/null
diff --git a/actionview/test/ujs/.gitignore b/actionview/test/ujs/.gitignore
deleted file mode 100644
index 31dbbff57c..0000000000
--- a/actionview/test/ujs/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/log
diff --git a/actionview/test/ujs/public/test/call-ajax.js b/actionview/test/ujs/public/test/call-ajax.js
index 49e64cad5c..4d0bfb0806 100644
--- a/actionview/test/ujs/public/test/call-ajax.js
+++ b/actionview/test/ujs/public/test/call-ajax.js
@@ -8,7 +8,6 @@ module('call-ajax', {
 })
 
 asyncTest('call ajax without "ajax:beforeSend"', 1, function() {
-
   var link = $('#qunit-fixture a')
   link.bindNative('click', function() {
     Rails.ajax({
@@ -21,7 +20,7 @@ asyncTest('call ajax without "ajax:beforeSend"', 1, function() {
   })
 
   link.triggerNative('click')
-  setTimeout(function() { start() }, 13)
+  setTimeout(function() { start() }, 50)
 })
 
 })()
diff --git a/actionview/test/ujs/server.rb b/actionview/test/ujs/server.rb
index 7d1bab4b2a..48e9bcb65f 100644
--- a/actionview/test/ujs/server.rb
+++ b/actionview/test/ujs/server.rb
@@ -23,18 +23,30 @@ module UJS
     config.public_file_server.enabled = true
     config.logger = Logger.new(STDOUT)
     config.log_level = :error
+
+    config.content_security_policy do |policy|
+      policy.default_src :self, :https
+      policy.font_src    :self, :https, :data
+      policy.img_src     :self, :https, :data
+      policy.object_src  :none
+      policy.script_src  :self, :https
+      policy.style_src   :self, :https
+    end
+
+    config.content_security_policy_nonce_generator = ->(req) { SecureRandom.base64(16) }
   end
 end
 
 module TestsHelper
   def test_to(*names)
-    names = ["/vendor/qunit.js", "settings"] + names
-    names.map { |name| script_tag name }.join("\n").html_safe
-  end
+    names = names.map { |name| "/test/#{name}.js" }
+    names = %w[/vendor/qunit.js /test/settings.js] + names
 
-  def script_tag(src)
-    src = "/test/#{src}.js" unless src.index("/")
-    %(<script src="#{src}" type="text/javascript"></script>).html_safe
+    capture do
+      names.each do |name|
+        concat(javascript_include_tag(name))
+      end
+    end
   end
 end
 
@@ -56,7 +68,7 @@ class TestsController < ActionController::Base
     elsif params[:iframe]
       payload = JSON.generate(data).gsub("<", "&lt;").gsub(">", "&gt;")
       html = <<-HTML
-        <script>
+        <script nonce="#{request.content_security_policy_nonce}">
           if (window.top && window.top !== window)
             window.top.jQuery.event.trigger('iframe:loaded', #{payload})
         </script>
diff --git a/actionview/test/ujs/views/layouts/application.html.erb b/actionview/test/ujs/views/layouts/application.html.erb
index c787e77b84..8f6f6fc17f 100644
--- a/actionview/test/ujs/views/layouts/application.html.erb
+++ b/actionview/test/ujs/views/layouts/application.html.erb
@@ -2,9 +2,10 @@
 <html id="html">
   <head>
     <title><%= @title %></title>
+    <%= csp_meta_tag %>
     <link href="/vendor/qunit.css" media="screen" rel="stylesheet" type="text/css" media="screen, projection" />
     <script src="/vendor/jquery-2.2.0.js" type="text/javascript"></script>
-    <script>
+    <%= javascript_tag nonce: true do %>
       // This is for test in override.js.
       // Must go before rails-ujs.
       document.addEventListener('rails:attachBindings', function() {
@@ -15,8 +16,8 @@
           e.preventDefault();
         });
       });
-    </script>
-    <%= script_tag "/rails-ujs.js" %>
+    <% end %>
+    <%= javascript_include_tag "/rails-ujs.js" %>
   </head>
 
   <body id="body">
diff --git a/activejob/CHANGELOG.md b/activejob/CHANGELOG.md
index 4453f845f4..c6a3ad8ade 100644
--- a/activejob/CHANGELOG.md
+++ b/activejob/CHANGELOG.md
@@ -1,12 +1,20 @@
-## Rails 5.2.0.beta2 (November 28, 2017) ##
+## Rails 6.0.0.alpha (Unreleased) ##
 
-*   No changes.
+*   Add support for timezones to Active Job
 
+    Record what was the current timezone in effect when the job was
+    enqueued and then restore when the job is executed in same way
+    that the current locale is recorded and restored.
 
-## Rails 5.2.0.beta1 (November 27, 2017) ##
+    *Andrew White*
 
-*   Support redis-rb 4.0.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
     *Jeremy Daer*
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activejob/CHANGELOG.md) for previous changes.
+*   Add support to define custom argument serializers.
+
+    *Evgenii Pecherkin*, *Rafael Mendonça França*
+
+
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activejob/CHANGELOG.md) for previous changes.
diff --git a/activejob/activejob.gemspec b/activejob/activejob.gemspec
index 71e32f695b..be6292f737 100644
--- a/activejob/activejob.gemspec
+++ b/activejob/activejob.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Job framework with pluggable queues."
   s.description = "Declare job classes that can be run by a variety of queueing backends."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activejob/lib/active_job.rb b/activejob/lib/active_job.rb
index 626abaa767..01fab4d918 100644
--- a/activejob/lib/active_job.rb
+++ b/activejob/lib/active_job.rb
@@ -33,6 +33,7 @@ module ActiveJob
 
   autoload :Base
   autoload :QueueAdapters
+  autoload :Serializers
   autoload :ConfiguredJob
   autoload :TestCase
   autoload :TestHelper
diff --git a/activejob/lib/active_job/arguments.rb b/activejob/lib/active_job/arguments.rb
index de11e7fcb1..86bb0c5540 100644
--- a/activejob/lib/active_job/arguments.rb
+++ b/activejob/lib/active_job/arguments.rb
@@ -14,8 +14,8 @@ module ActiveJob
   end
 
   # Raised when an unsupported argument type is set as a job argument. We
-  # currently support NilClass, Integer, Fixnum, Float, String, TrueClass, FalseClass,
-  # Bignum, BigDecimal, and objects that can be represented as GlobalIDs (ex: Active Record).
+  # currently support NilClass, Integer, Float, String, TrueClass, FalseClass,
+  # BigDecimal, and objects that can be represented as GlobalIDs (ex: Active Record).
   # Raised if you set the key for a Hash something else than a string or
   # a symbol. Also raised when trying to serialize an object which can't be
   # identified with a Global ID - such as an unpersisted Active Record model.
@@ -25,7 +25,6 @@ module ActiveJob
     extend self
     # :nodoc:
     TYPE_WHITELIST = [ NilClass, String, Integer, Float, BigDecimal, TrueClass, FalseClass ]
-    TYPE_WHITELIST.push(Fixnum, Bignum) unless 1.class == Integer
 
     # Serializes a set of arguments. Whitelisted types are returned
     # as-is. Arrays/Hashes are serialized element by element.
@@ -44,13 +43,24 @@ module ActiveJob
     end
 
     private
+
       # :nodoc:
       GLOBALID_KEY = "_aj_globalid".freeze
       # :nodoc:
       SYMBOL_KEYS_KEY = "_aj_symbol_keys".freeze
       # :nodoc:
       WITH_INDIFFERENT_ACCESS_KEY = "_aj_hash_with_indifferent_access".freeze
-      private_constant :GLOBALID_KEY, :SYMBOL_KEYS_KEY, :WITH_INDIFFERENT_ACCESS_KEY
+      # :nodoc:
+      OBJECT_SERIALIZER_KEY = "_aj_serialized"
+
+      # :nodoc:
+      RESERVED_KEYS = [
+        GLOBALID_KEY, GLOBALID_KEY.to_sym,
+        SYMBOL_KEYS_KEY, SYMBOL_KEYS_KEY.to_sym,
+        OBJECT_SERIALIZER_KEY, OBJECT_SERIALIZER_KEY.to_sym,
+        WITH_INDIFFERENT_ACCESS_KEY, WITH_INDIFFERENT_ACCESS_KEY.to_sym,
+      ]
+      private_constant :RESERVED_KEYS
 
       def serialize_argument(argument)
         case argument
@@ -70,7 +80,7 @@ module ActiveJob
           result[SYMBOL_KEYS_KEY] = symbol_keys
           result
         else
-          raise SerializationError.new("Unsupported argument type: #{argument.class.name}")
+          Serializers.serialize(argument)
         end
       end
 
@@ -85,6 +95,8 @@ module ActiveJob
         when Hash
           if serialized_global_id?(argument)
             deserialize_global_id argument
+          elsif custom_serialized?(argument)
+            Serializers.deserialize(argument)
           else
             deserialize_hash(argument)
           end
@@ -101,6 +113,10 @@ module ActiveJob
         GlobalID::Locator.locate hash[GLOBALID_KEY]
       end
 
+      def custom_serialized?(hash)
+        hash.key?(OBJECT_SERIALIZER_KEY)
+      end
+
       def serialize_hash(argument)
         argument.each_with_object({}) do |(key, value), hash|
           hash[serialize_hash_key(key)] = serialize_argument(value)
@@ -117,14 +133,6 @@ module ActiveJob
         result
       end
 
-      # :nodoc:
-      RESERVED_KEYS = [
-        GLOBALID_KEY, GLOBALID_KEY.to_sym,
-        SYMBOL_KEYS_KEY, SYMBOL_KEYS_KEY.to_sym,
-        WITH_INDIFFERENT_ACCESS_KEY, WITH_INDIFFERENT_ACCESS_KEY.to_sym,
-      ]
-      private_constant :RESERVED_KEYS
-
       def serialize_hash_key(key)
         case key
         when *RESERVED_KEYS
diff --git a/activejob/lib/active_job/base.rb b/activejob/lib/active_job/base.rb
index ae112abb2c..2b2a59e969 100644
--- a/activejob/lib/active_job/base.rb
+++ b/activejob/lib/active_job/base.rb
@@ -9,6 +9,7 @@ require "active_job/execution"
 require "active_job/callbacks"
 require "active_job/exceptions"
 require "active_job/logging"
+require "active_job/timezones"
 require "active_job/translation"
 
 module ActiveJob #:nodoc:
@@ -59,6 +60,7 @@ module ActiveJob #:nodoc:
   # * SerializationError - Error class for serialization errors.
   class Base
     include Core
+    include Serializers
     include QueueAdapter
     include QueueName
     include QueuePriority
@@ -67,6 +69,7 @@ module ActiveJob #:nodoc:
     include Callbacks
     include Exceptions
     include Logging
+    include Timezones
     include Translation
 
     ActiveSupport.run_load_hooks(:active_job, self)
diff --git a/activejob/lib/active_job/core.rb b/activejob/lib/active_job/core.rb
index 879746fc01..da841ae45b 100644
--- a/activejob/lib/active_job/core.rb
+++ b/activejob/lib/active_job/core.rb
@@ -31,6 +31,9 @@ module ActiveJob
 
       # I18n.locale to be used during the job.
       attr_accessor :locale
+
+      # Timezone to be used during the job.
+      attr_accessor :timezone
     end
 
     # These methods will be included into any Active Job object, adding
@@ -87,7 +90,8 @@ module ActiveJob
         "priority"   => priority,
         "arguments"  => serialize_arguments(arguments),
         "executions" => executions,
-        "locale"     => I18n.locale.to_s
+        "locale"     => I18n.locale.to_s,
+        "timezone"   => Time.zone.try(:name)
       }
     end
 
@@ -125,6 +129,7 @@ module ActiveJob
       self.serialized_arguments = job_data["arguments"]
       self.executions           = job_data["executions"]
       self.locale               = job_data["locale"] || I18n.locale.to_s
+      self.timezone             = job_data["timezone"] || Time.zone.try(:name)
     end
 
     private
diff --git a/activejob/lib/active_job/exceptions.rb b/activejob/lib/active_job/exceptions.rb
index 8b4a88ba6a..ae700848d0 100644
--- a/activejob/lib/active_job/exceptions.rb
+++ b/activejob/lib/active_job/exceptions.rb
@@ -61,18 +61,28 @@ module ActiveJob
       # Discard the job with no attempts to retry, if the exception is raised. This is useful when the subject of the job,
       # like an Active Record, is no longer available, and the job is thus no longer relevant.
       #
+      # You can also pass a block that'll be invoked. This block is yielded with the job instance as the first and the error instance as the second parameter.
+      #
       # ==== Example
       #
       #  class SearchIndexingJob < ActiveJob::Base
       #    discard_on ActiveJob::DeserializationError
+      #    discard_on(CustomAppException) do |job, exception|
+      #      ExceptionNotifier.caught(exception)
+      #    end
       #
       #    def perform(record)
       #      # Will raise ActiveJob::DeserializationError if the record can't be deserialized
+      #      # Might raise CustomAppException for something domain specific
       #    end
       #  end
       def discard_on(exception)
         rescue_from exception do |error|
-          logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}."
+          if block_given?
+            yield self, exception
+          else
+            logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}."
+          end
         end
       end
     end
diff --git a/activejob/lib/active_job/gem_version.rb b/activejob/lib/active_job/gem_version.rb
index 49dfd4095e..770f70dc5e 100644
--- a/activejob/lib/active_job/gem_version.rb
+++ b/activejob/lib/active_job/gem_version.rb
@@ -7,10 +7,10 @@ module ActiveJob
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activejob/lib/active_job/logging.rb b/activejob/lib/active_job/logging.rb
index f53b7eaee5..3312857ac7 100644
--- a/activejob/lib/active_job/logging.rb
+++ b/activejob/lib/active_job/logging.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/hash/transform_values"
 require "active_support/core_ext/string/filters"
 require "active_support/tagged_logging"
 require "active_support/logger"
@@ -12,13 +11,13 @@ module ActiveJob
     included do
       cattr_accessor :logger, default: ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(STDOUT))
 
-      around_enqueue do |_, block, _|
+      around_enqueue do |_, block|
         tag_logger do
           block.call
         end
       end
 
-      around_perform do |job, block, _|
+      around_perform do |job, block|
         tag_logger(job.class.name, job.job_id) do
           payload = { adapter: job.class.queue_adapter, job: job }
           ActiveSupport::Notifications.instrument("perform_start.active_job", payload.dup)
diff --git a/activejob/lib/active_job/railtie.rb b/activejob/lib/active_job/railtie.rb
index 7b0742a6d2..d0294854d3 100644
--- a/activejob/lib/active_job/railtie.rb
+++ b/activejob/lib/active_job/railtie.rb
@@ -7,17 +7,28 @@ module ActiveJob
   # = Active Job Railtie
   class Railtie < Rails::Railtie # :nodoc:
     config.active_job = ActiveSupport::OrderedOptions.new
+    config.active_job.custom_serializers = []
 
     initializer "active_job.logger" do
       ActiveSupport.on_load(:active_job) { self.logger = ::Rails.logger }
     end
 
+    initializer "active_job.custom_serializers" do |app|
+      config.after_initialize do
+        custom_serializers = app.config.active_job.delete(:custom_serializers)
+        ActiveJob::Serializers.add_serializers custom_serializers
+      end
+    end
+
     initializer "active_job.set_configs" do |app|
       options = app.config.active_job
       options.queue_adapter ||= :async
 
       ActiveSupport.on_load(:active_job) do
-        options.each { |k, v| send("#{k}=", v) }
+        options.each do  |k, v|
+          k = "#{k}="
+          send(k, v) if respond_to? k
+        end
       end
     end
 
diff --git a/activejob/lib/active_job/serializers.rb b/activejob/lib/active_job/serializers.rb
new file mode 100644
index 0000000000..df66e66659
--- /dev/null
+++ b/activejob/lib/active_job/serializers.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+require "set"
+
+module ActiveJob
+  # The <tt>ActiveJob::Serializers</tt> module is used to store a list of known serializers
+  # and to add new ones. It also has helpers to serialize/deserialize objects.
+  module Serializers # :nodoc:
+    extend ActiveSupport::Autoload
+    extend ActiveSupport::Concern
+
+    autoload :ObjectSerializer
+    autoload :SymbolSerializer
+    autoload :DurationSerializer
+    autoload :DateTimeSerializer
+    autoload :DateSerializer
+    autoload :TimeWithZoneSerializer
+    autoload :TimeSerializer
+
+    mattr_accessor :_additional_serializers
+    self._additional_serializers = Set.new
+
+    class << self
+      # Returns serialized representative of the passed object.
+      # Will look up through all known serializers.
+      # Raises <tt>ActiveJob::SerializationError</tt> if it can't find a proper serializer.
+      def serialize(argument)
+        serializer = serializers.detect { |s| s.serialize?(argument) }
+        raise SerializationError.new("Unsupported argument type: #{argument.class.name}") unless serializer
+        serializer.serialize(argument)
+      end
+
+      # Returns deserialized object.
+      # Will look up through all known serializers.
+      # If no serializer found will raise <tt>ArgumentError</tt>.
+      def deserialize(argument)
+        serializer_name = argument[Arguments::OBJECT_SERIALIZER_KEY]
+        raise ArgumentError, "Serializer name is not present in the argument: #{argument.inspect}" unless serializer_name
+
+        serializer = serializer_name.safe_constantize
+        raise ArgumentError, "Serializer #{serializer_name} is not known" unless serializer
+
+        serializer.deserialize(argument)
+      end
+
+      # Returns list of known serializers.
+      def serializers
+        self._additional_serializers
+      end
+
+      # Adds new serializers to a list of known serializers.
+      def add_serializers(*new_serializers)
+        self._additional_serializers += new_serializers.flatten
+      end
+    end
+
+    add_serializers SymbolSerializer,
+      DurationSerializer,
+      DateTimeSerializer,
+      DateSerializer,
+      TimeWithZoneSerializer,
+      TimeSerializer
+  end
+end
diff --git a/activejob/lib/active_job/serializers/date_serializer.rb b/activejob/lib/active_job/serializers/date_serializer.rb
new file mode 100644
index 0000000000..e995d30faa
--- /dev/null
+++ b/activejob/lib/active_job/serializers/date_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class DateSerializer < ObjectSerializer # :nodoc:
+      def serialize(date)
+        super("value" => date.iso8601)
+      end
+
+      def deserialize(hash)
+        Date.iso8601(hash["value"])
+      end
+
+      private
+
+        def klass
+          Date
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/date_time_serializer.rb b/activejob/lib/active_job/serializers/date_time_serializer.rb
new file mode 100644
index 0000000000..fe780a1978
--- /dev/null
+++ b/activejob/lib/active_job/serializers/date_time_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class DateTimeSerializer < ObjectSerializer # :nodoc:
+      def serialize(time)
+        super("value" => time.iso8601)
+      end
+
+      def deserialize(hash)
+        DateTime.iso8601(hash["value"])
+      end
+
+      private
+
+        def klass
+          DateTime
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/duration_serializer.rb b/activejob/lib/active_job/serializers/duration_serializer.rb
new file mode 100644
index 0000000000..715fe27a5c
--- /dev/null
+++ b/activejob/lib/active_job/serializers/duration_serializer.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class DurationSerializer < ObjectSerializer # :nodoc:
+      def serialize(duration)
+        super("value" => duration.value, "parts" => Arguments.serialize(duration.parts))
+      end
+
+      def deserialize(hash)
+        value = hash["value"]
+        parts = Arguments.deserialize(hash["parts"])
+
+        klass.new(value, parts)
+      end
+
+      private
+
+        def klass
+          ActiveSupport::Duration
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/object_serializer.rb b/activejob/lib/active_job/serializers/object_serializer.rb
new file mode 100644
index 0000000000..1dfd1e44be
--- /dev/null
+++ b/activejob/lib/active_job/serializers/object_serializer.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    # Base class for serializing and deserializing custom objects.
+    #
+    # Example:
+    #
+    #   class MoneySerializer < ActiveJob::Serializers::ObjectSerializer
+    #     def serialize(money)
+    #       super("amount" => money.amount, "currency" => money.currency)
+    #     end
+    #
+    #     def deserialize(hash)
+    #       Money.new(hash["amount"], hash["currency"])
+    #     end
+    #
+    #     private
+    #
+    #       def klass
+    #         Money
+    #       end
+    #   end
+    class ObjectSerializer
+      include Singleton
+
+      class << self
+        delegate :serialize?, :serialize, :deserialize, to: :instance
+      end
+
+      # Determines if an argument should be serialized by a serializer.
+      def serialize?(argument)
+        argument.is_a?(klass)
+      end
+
+      # Serializes an argument to a JSON primitive type.
+      def serialize(hash)
+        { Arguments::OBJECT_SERIALIZER_KEY => self.class.name }.merge!(hash)
+      end
+
+      # Deserilizes an argument form a JSON primiteve type.
+      def deserialize(_argument)
+        raise NotImplementedError
+      end
+
+      private
+
+        # The class of the object that will be serialized.
+        def klass # :doc:
+          raise NotImplementedError
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/symbol_serializer.rb b/activejob/lib/active_job/serializers/symbol_serializer.rb
new file mode 100644
index 0000000000..7e1f9553a2
--- /dev/null
+++ b/activejob/lib/active_job/serializers/symbol_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class SymbolSerializer < ObjectSerializer # :nodoc:
+      def serialize(argument)
+        super("value" => argument.to_s)
+      end
+
+      def deserialize(argument)
+        argument["value"].to_sym
+      end
+
+      private
+
+        def klass
+          Symbol
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/time_serializer.rb b/activejob/lib/active_job/serializers/time_serializer.rb
new file mode 100644
index 0000000000..fe20772f35
--- /dev/null
+++ b/activejob/lib/active_job/serializers/time_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class TimeSerializer < ObjectSerializer # :nodoc:
+      def serialize(time)
+        super("value" => time.iso8601)
+      end
+
+      def deserialize(hash)
+        Time.iso8601(hash["value"])
+      end
+
+      private
+
+        def klass
+          Time
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/serializers/time_with_zone_serializer.rb b/activejob/lib/active_job/serializers/time_with_zone_serializer.rb
new file mode 100644
index 0000000000..43017fc75b
--- /dev/null
+++ b/activejob/lib/active_job/serializers/time_with_zone_serializer.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Serializers
+    class TimeWithZoneSerializer < ObjectSerializer # :nodoc:
+      def serialize(time)
+        super("value" => time.iso8601)
+      end
+
+      def deserialize(hash)
+        Time.iso8601(hash["value"]).in_time_zone
+      end
+
+      private
+
+        def klass
+          ActiveSupport::TimeWithZone
+        end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/timezones.rb b/activejob/lib/active_job/timezones.rb
new file mode 100644
index 0000000000..ac018eb752
--- /dev/null
+++ b/activejob/lib/active_job/timezones.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Timezones #:nodoc:
+    extend ActiveSupport::Concern
+
+    included do
+      around_perform do |job, block|
+        Time.use_zone(job.timezone, &block)
+      end
+    end
+  end
+end
diff --git a/activejob/lib/active_job/translation.rb b/activejob/lib/active_job/translation.rb
index fb45c80d67..0fd9b9fc06 100644
--- a/activejob/lib/active_job/translation.rb
+++ b/activejob/lib/active_job/translation.rb
@@ -5,7 +5,7 @@ module ActiveJob
     extend ActiveSupport::Concern
 
     included do
-      around_perform do |job, block, _|
+      around_perform do |job, block|
         I18n.with_locale(job.locale, &block)
       end
     end
diff --git a/activejob/test/cases/argument_serialization_test.rb b/activejob/test/cases/argument_serialization_test.rb
index 7e7f854da0..e5f1f087fe 100644
--- a/activejob/test/cases/argument_serialization_test.rb
+++ b/activejob/test/cases/argument_serialization_test.rb
@@ -13,6 +13,9 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
 
   [ nil, 1, 1.0, 1_000_000_000_000_000_000_000,
     "a", true, false, BigDecimal(5),
+    :a, 1.day, Date.new(2001, 2, 3), Time.new(2002, 10, 31, 2, 2, 2, "+02:00"),
+    DateTime.new(2001, 2, 3, 4, 5, 6, "+03:00"),
+    ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"]),
     [ 1, "a" ],
     { "a" => 1 }
   ].each do |arg|
@@ -21,7 +24,7 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     end
   end
 
-  [ :a, Object.new, self, Person.find("5").to_gid ].each do |arg|
+  [ Object.new, self, Person.find("5").to_gid ].each do |arg|
     test "does not serialize #{arg.class}" do
       assert_raises ActiveJob::SerializationError do
         ActiveJob::Arguments.serialize [ arg ]
@@ -46,6 +49,49 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     assert_arguments_roundtrip([a: 1, "b" => 2])
   end
 
+  test "serialize a hash" do
+    symbol_key = { a: 1 }
+    string_key = { "a" => 1 }
+    indifferent_access = { a: 1 }.with_indifferent_access
+
+    assert_equal(
+      { "a" => 1, "_aj_symbol_keys" => ["a"] },
+      ActiveJob::Arguments.serialize([symbol_key]).first
+    )
+    assert_equal(
+      { "a" => 1, "_aj_symbol_keys" => [] },
+      ActiveJob::Arguments.serialize([string_key]).first
+    )
+    assert_equal(
+      { "a" => 1, "_aj_hash_with_indifferent_access" => true },
+      ActiveJob::Arguments.serialize([indifferent_access]).first
+    )
+  end
+
+  test "deserialize a hash" do
+    symbol_key = { "a" => 1, "_aj_symbol_keys" => ["a"] }
+    string_key = { "a" => 1, "_aj_symbol_keys" => [] }
+    another_string_key = { "a" => 1 }
+    indifferent_access = { "a" => 1, "_aj_hash_with_indifferent_access" => true }
+
+    assert_equal(
+      { a: 1 },
+      ActiveJob::Arguments.deserialize([symbol_key]).first
+    )
+    assert_equal(
+      { "a" => 1 },
+      ActiveJob::Arguments.deserialize([string_key]).first
+    )
+    assert_equal(
+      { "a" => 1 },
+      ActiveJob::Arguments.deserialize([another_string_key]).first
+    )
+    assert_equal(
+      { "a" => 1 },
+      ActiveJob::Arguments.deserialize([indifferent_access]).first
+    )
+  end
+
   test "should maintain hash with indifferent access" do
     symbol_key = { a: 1 }
     string_key = { "a" => 1 }
@@ -56,6 +102,14 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, perform_round_trip([indifferent_access]).first
   end
 
+  test "should maintain time with zone" do
+    Time.use_zone "Alaska" do
+      time_with_zone = Time.new(2002, 10, 31, 2, 2, 2).in_time_zone
+      assert_instance_of ActiveSupport::TimeWithZone, perform_round_trip([time_with_zone]).first
+      assert_arguments_unchanged time_with_zone
+    end
+  end
+
   test "should disallow non-string/symbol hash keys" do
     assert_raises ActiveJob::SerializationError do
       ActiveJob::Arguments.serialize [ { 1 => 2 } ]
diff --git a/activejob/test/cases/exceptions_test.rb b/activejob/test/cases/exceptions_test.rb
index 22fed0a808..bc33d79f61 100644
--- a/activejob/test/cases/exceptions_test.rb
+++ b/activejob/test/cases/exceptions_test.rb
@@ -58,6 +58,13 @@ class ExceptionsTest < ActiveJob::TestCase
     end
   end
 
+  test "custom handling of discarded job" do
+    perform_enqueued_jobs do
+      RetryJob.perform_later "CustomDiscardableError", 2
+      assert_equal "Dealt with a job that was discarded in a custom way", JobBuffer.last_value
+    end
+  end
+
   test "custom handling of job that exceeds retry attempts" do
     perform_enqueued_jobs do
       RetryJob.perform_later "CustomCatchError", 6
diff --git a/activejob/test/cases/job_serialization_test.rb b/activejob/test/cases/job_serialization_test.rb
index 440051c427..5c9994508e 100644
--- a/activejob/test/cases/job_serialization_test.rb
+++ b/activejob/test/cases/job_serialization_test.rb
@@ -54,4 +54,11 @@ class JobSerializationTest < ActiveSupport::TestCase
     job.provider_job_id = "some value set by adapter"
     assert_equal job.provider_job_id, job.serialize["provider_job_id"]
   end
+
+  test "serialize stores the current timezone" do
+    Time.use_zone "Hawaii" do
+      job = HelloJob.new
+      assert_equal "Hawaii", job.serialize["timezone"]
+    end
+  end
 end
diff --git a/activejob/test/cases/serializers_test.rb b/activejob/test/cases/serializers_test.rb
new file mode 100644
index 0000000000..bee0c061bd
--- /dev/null
+++ b/activejob/test/cases/serializers_test.rb
@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+require "helper"
+require "active_job/serializers"
+
+class SerializersTest < ActiveSupport::TestCase
+  class DummyValueObject
+    attr_accessor :value
+
+    def initialize(value)
+      @value = value
+    end
+
+    def ==(other)
+      self.value == other.value
+    end
+  end
+
+  class DummySerializer < ActiveJob::Serializers::ObjectSerializer
+    def serialize(object)
+      super({ "value" => object.value })
+    end
+
+    def deserialize(hash)
+      DummyValueObject.new(hash["value"])
+    end
+
+    private
+
+      def klass
+        DummyValueObject
+      end
+  end
+
+  setup do
+    @value_object = DummyValueObject.new 123
+    @original_serializers = ActiveJob::Serializers.serializers
+  end
+
+  teardown do
+    ActiveJob::Serializers._additional_serializers = @original_serializers
+  end
+
+  test "can't serialize unknown object" do
+    assert_raises ActiveJob::SerializationError do
+      ActiveJob::Serializers.serialize @value_object
+    end
+  end
+
+  test "will serialize objects with serializers registered" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+
+    assert_equal(
+      { "_aj_serialized" => "SerializersTest::DummySerializer", "value" => 123 },
+      ActiveJob::Serializers.serialize(@value_object)
+    )
+  end
+
+  test "won't deserialize unknown hash" do
+    hash = { "_dummy_serializer" => 123, "_aj_symbol_keys" => [] }
+    error = assert_raises(ArgumentError) do
+      ActiveJob::Serializers.deserialize(hash)
+    end
+    assert_equal(
+      'Serializer name is not present in the argument: {"_dummy_serializer"=>123, "_aj_symbol_keys"=>[]}',
+      error.message
+    )
+  end
+
+  test "won't deserialize unknown serializer" do
+    hash = { "_aj_serialized" => "DoNotExist", "value" => 123 }
+    error = assert_raises(ArgumentError) do
+      ActiveJob::Serializers.deserialize(hash)
+    end
+    assert_equal(
+      "Serializer DoNotExist is not known",
+      error.message
+    )
+  end
+
+  test "will deserialize know serialized objects" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+    hash = { "_aj_serialized" => "SerializersTest::DummySerializer", "value" => 123 }
+    assert_equal DummyValueObject.new(123), ActiveJob::Serializers.deserialize(hash)
+  end
+
+  test "adds new serializer" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+    assert ActiveJob::Serializers.serializers.include?(DummySerializer)
+  end
+
+  test "can't add serializer with the same key twice" do
+    ActiveJob::Serializers.add_serializers DummySerializer
+    assert_no_difference(-> { ActiveJob::Serializers.serializers.size }) do
+      ActiveJob::Serializers.add_serializers DummySerializer
+    end
+  end
+end
diff --git a/activejob/test/cases/timezones_test.rb b/activejob/test/cases/timezones_test.rb
new file mode 100644
index 0000000000..e2095b020d
--- /dev/null
+++ b/activejob/test/cases/timezones_test.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "helper"
+require "jobs/timezone_dependent_job"
+
+class TimezonesTest < ActiveSupport::TestCase
+  setup do
+    JobBuffer.clear
+  end
+
+  test "it performs the job in the given timezone" do
+    job = TimezoneDependentJob.new("2018-01-01T00:00:00Z")
+    job.timezone = "London"
+    job.perform_now
+
+    assert_equal "Happy New Year!", JobBuffer.last_value
+
+    job = TimezoneDependentJob.new("2018-01-01T00:00:00Z")
+    job.timezone = "Eastern Time (US & Canada)"
+    job.perform_now
+
+    assert_equal "Just 5 hours to go", JobBuffer.last_value
+  end
+end
diff --git a/activejob/test/integration/queuing_test.rb b/activejob/test/integration/queuing_test.rb
index 32ef485c45..7a95d3d039 100644
--- a/activejob/test/integration/queuing_test.rb
+++ b/activejob/test/integration/queuing_test.rb
@@ -110,6 +110,22 @@ class QueuingTest < ActiveSupport::TestCase
     end
   end
 
+  test "current timezone is kept while running perform_later" do
+    skip if adapter_is?(:inline)
+
+    begin
+      current_zone = Time.zone
+      Time.zone = "Hawaii"
+
+      TestJob.perform_later @id
+      wait_for_jobs_to_finish_for(5.seconds)
+      assert job_executed
+      assert_equal "Hawaii", job_executed_in_timezone
+    ensure
+      Time.zone = current_zone
+    end
+  end
+
   test "should run job with higher priority first" do
     skip unless adapter_is?(:delayed_job, :que)
 
diff --git a/activejob/test/jobs/retry_job.rb b/activejob/test/jobs/retry_job.rb
index 9aa99d9a21..82b80fe12b 100644
--- a/activejob/test/jobs/retry_job.rb
+++ b/activejob/test/jobs/retry_job.rb
@@ -10,6 +10,7 @@ class ExponentialWaitTenAttemptsError < StandardError; end
 class CustomWaitTenAttemptsError < StandardError; end
 class CustomCatchError < StandardError; end
 class DiscardableError < StandardError; end
+class CustomDiscardableError < StandardError; end
 
 class RetryJob < ActiveJob::Base
   retry_on DefaultsError
@@ -19,6 +20,7 @@ class RetryJob < ActiveJob::Base
   retry_on CustomWaitTenAttemptsError, wait: ->(executions) { executions * 2 }, attempts: 10
   retry_on(CustomCatchError) { |job, exception| JobBuffer.add("Dealt with a job that failed to retry in a custom way after #{job.arguments.second} attempts. Message: #{exception.message}") }
   discard_on DiscardableError
+  discard_on(CustomDiscardableError) { |job, exception| JobBuffer.add("Dealt with a job that was discarded in a custom way") }
 
   def perform(raising, attempts)
     if executions < attempts
diff --git a/activejob/test/jobs/timezone_dependent_job.rb b/activejob/test/jobs/timezone_dependent_job.rb
new file mode 100644
index 0000000000..41f473d533
--- /dev/null
+++ b/activejob/test/jobs/timezone_dependent_job.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require_relative "../support/job_buffer"
+
+class TimezoneDependentJob < ActiveJob::Base
+  def perform(now)
+    now = now.in_time_zone
+    new_year = localtime(2018, 1, 1)
+
+    if now >= new_year
+      JobBuffer.add("Happy New Year!")
+    else
+      JobBuffer.add("Just #{(new_year - now).div(3600)} hours to go")
+    end
+  end
+
+  private
+
+    def localtime(*args)
+      Time.zone ? Time.zone.local(*args) : Time.utc(*args)
+    end
+end
diff --git a/activejob/test/support/integration/dummy_app_template.rb b/activejob/test/support/integration/dummy_app_template.rb
index 7ea78c3350..b56dd3e591 100644
--- a/activejob/test/support/integration/dummy_app_template.rb
+++ b/activejob/test/support/integration/dummy_app_template.rb
@@ -21,6 +21,7 @@ class TestJob < ActiveJob::Base
     File.open(Rails.root.join("tmp/\#{x}.new"), "wb+") do |f|
       f.write Marshal.dump({
         "locale" => I18n.locale.to_s || "en",
+        "timezone" => Time.zone.try(:name) || "UTC",
         "executed_at" => Time.now.to_r
       })
     end
diff --git a/activejob/test/support/integration/test_case_helpers.rb b/activejob/test/support/integration/test_case_helpers.rb
index f02a32a38e..3d9b265b66 100644
--- a/activejob/test/support/integration/test_case_helpers.rb
+++ b/activejob/test/support/integration/test_case_helpers.rb
@@ -62,4 +62,8 @@ module TestCaseHelpers
     def job_executed_in_locale(id = @id)
       job_data(id)["locale"]
     end
+
+    def job_executed_in_timezone(id = @id)
+      job_data(id)["timezone"]
+    end
 end
diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index b67a803b9d..b28c83e4ed 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,60 +1,8 @@
-*   Fix to working before/after validation callbacks on multiple contexts.
+## Rails 6.0.0.alpha (Unreleased) ##
 
-    *Yoshiyuki Hirano*
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-## Rails 5.2.0.beta2 (November 28, 2017) ##
+    *Jeremy Daer*
 
-*   No changes.
 
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Execute `ConfirmationValidator` validation when `_confirmation`'s value is `false`.
-
-    *bogdanvlviv*
-
-*   Allow passing a Proc or Symbol to length validator options.
-
-    *Matt Rohrer*
-
-*   Add method `#merge!` for `ActiveModel::Errors`.
-
-    *Jahfer Husain*
-
-*   Fix regression in numericality validator when comparing Decimal and Float input
-    values with more scale than the schema.
-
-    *Bradley Priest*
-
-*   Fix methods `#keys`, `#values` in `ActiveModel::Errors`.
-
-    Change `#keys` to only return the keys that don't have empty messages.
-
-    Change `#values` to only return the not empty values.
-
-    Example:
-
-        # Before
-        person = Person.new
-        person.errors.keys     # => []
-        person.errors.values   # => []
-        person.errors.messages # => {}
-        person.errors[:name]   # => []
-        person.errors.messages # => {:name => []}
-        person.errors.keys     # => [:name]
-        person.errors.values   # => [[]]
-
-        # After
-        person = Person.new
-        person.errors.keys     # => []
-        person.errors.values   # => []
-        person.errors.messages # => {}
-        person.errors[:name]   # => []
-        person.errors.messages # => {:name => []}
-        person.errors.keys     # => []
-        person.errors.values   # => []
-
-    *bogdanvlviv*
-
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activemodel/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activemodel/CHANGELOG.md) for previous changes.
diff --git a/activemodel/activemodel.gemspec b/activemodel/activemodel.gemspec
index a070a2898c..7be466dc4c 100644
--- a/activemodel/activemodel.gemspec
+++ b/activemodel/activemodel.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "A toolkit for building modeling frameworks (part of Rails)."
   s.description = "A toolkit for building modeling frameworks like Active Record. Rich support for attributes, callbacks, validations, serialization, internationalization, and testing."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activemodel/lib/active_model/attribute/user_provided_default.rb b/activemodel/lib/active_model/attribute/user_provided_default.rb
index f274b687d4..a5dc6188d2 100644
--- a/activemodel/lib/active_model/attribute/user_provided_default.rb
+++ b/activemodel/lib/active_model/attribute/user_provided_default.rb
@@ -22,6 +22,28 @@ module ActiveModel
         self.class.new(name, user_provided_value, type, original_attribute)
       end
 
+      def marshal_dump
+        result = [
+          name,
+          value_before_type_cast,
+          type,
+          original_attribute,
+        ]
+        result << value if defined?(@value)
+        result
+      end
+
+      def marshal_load(values)
+        name, user_provided_value, type, original_attribute, value = values
+        @name = name
+        @user_provided_value = user_provided_value
+        @type = type
+        @original_attribute = original_attribute
+        if values.length == 5
+          @value = value
+        end
+      end
+
       protected
 
         attr_reader :user_provided_value
diff --git a/activemodel/lib/active_model/attribute_mutation_tracker.rb b/activemodel/lib/active_model/attribute_mutation_tracker.rb
index c67e1b809a..8e92c8807f 100644
--- a/activemodel/lib/active_model/attribute_mutation_tracker.rb
+++ b/activemodel/lib/active_model/attribute_mutation_tracker.rb
@@ -35,6 +35,10 @@ module ActiveModel
       end
     end
 
+    def changed_attribute_names
+      attr_names.select { |attr| changed?(attr) }
+    end
+
     def any_changes?
       attr_names.any? { |attr| changed?(attr) }
     end
@@ -65,13 +69,8 @@ module ActiveModel
       forced_changes << attr_name.to_s
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
-
-      attr_reader :attributes, :forced_changes
-
     private
+      attr_reader :attributes, :forced_changes
 
       def attr_names
         attributes.keys
@@ -109,8 +108,5 @@ module ActiveModel
 
     def original_value(*)
     end
-
-    def force_change(*)
-    end
   end
 end
diff --git a/activemodel/lib/active_model/attribute_set/builder.rb b/activemodel/lib/active_model/attribute_set/builder.rb
index 758eb830fc..bf2d06b48a 100644
--- a/activemodel/lib/active_model/attribute_set/builder.rb
+++ b/activemodel/lib/active_model/attribute_set/builder.rb
@@ -22,12 +22,12 @@ module ActiveModel
   class LazyAttributeHash # :nodoc:
     delegate :transform_values, :each_key, :each_value, :fetch, :except, to: :materialize
 
-    def initialize(types, values, additional_types, default_attributes)
+    def initialize(types, values, additional_types, default_attributes, delegate_hash = {})
       @types = types
       @values = values
       @additional_types = additional_types
       @materialized = false
-      @delegate_hash = {}
+      @delegate_hash = delegate_hash
       @default_attributes = default_attributes
     end
 
@@ -76,15 +76,17 @@ module ActiveModel
     end
 
     def marshal_dump
-      materialize
+      [@types, @values, @additional_types, @default_attributes, @delegate_hash]
     end
 
-    def marshal_load(delegate_hash)
-      @delegate_hash = delegate_hash
-      @types = {}
-      @values = {}
-      @additional_types = {}
-      @materialized = true
+    def marshal_load(values)
+      if values.is_a?(Hash)
+        empty_hash = {}.freeze
+        initialize(empty_hash, empty_hash, empty_hash, empty_hash, values)
+        @materialized = true
+      else
+        initialize(*values)
+      end
     end
 
     protected
diff --git a/activemodel/lib/active_model/attributes.rb b/activemodel/lib/active_model/attributes.rb
index 28dd24b3cd..046ae67ad7 100644
--- a/activemodel/lib/active_model/attributes.rb
+++ b/activemodel/lib/active_model/attributes.rb
@@ -23,7 +23,7 @@ module ActiveModel
         end
         self.attribute_types = attribute_types.merge(name => type)
         define_default_attribute(name, options.fetch(:default, NO_DEFAULT_PROVIDED), type)
-        define_attribute_methods(name)
+        define_attribute_method(name)
       end
 
       private
diff --git a/activemodel/lib/active_model/dirty.rb b/activemodel/lib/active_model/dirty.rb
index d2ebd18107..0044fde6c5 100644
--- a/activemodel/lib/active_model/dirty.rb
+++ b/activemodel/lib/active_model/dirty.rb
@@ -3,6 +3,7 @@
 require "active_support/hash_with_indifferent_access"
 require "active_support/core_ext/object/duplicable"
 require "active_model/attribute_mutation_tracker"
+require "active_model/attribute_set"
 
 module ActiveModel
   # == Active \Model \Dirty
@@ -142,9 +143,8 @@ module ActiveModel
     end
 
     def changes_applied # :nodoc:
-      @previously_changed = changes
+      _prepare_changes
       @mutations_before_last_save = mutations_from_database
-      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
       forget_attribute_assignments
       @mutations_from_database = nil
     end
@@ -155,7 +155,7 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changed? # => true
     def changed?
-      changed_attributes.present?
+      mutations_from_database.any_changes?
     end
 
     # Returns an array with the name of the attributes with unsaved changes.
@@ -164,24 +164,24 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changed # => ["name"]
     def changed
-      changed_attributes.keys
+      mutations_from_database.changed_attribute_names
     end
 
     # Handles <tt>*_changed?</tt> for +method_missing+.
     def attribute_changed?(attr, from: OPTION_NOT_GIVEN, to: OPTION_NOT_GIVEN) # :nodoc:
-      !!changes_include?(attr) &&
+      !!mutations_from_database.changed?(attr) &&
         (to == OPTION_NOT_GIVEN || to == _read_attribute(attr)) &&
-        (from == OPTION_NOT_GIVEN || from == changed_attributes[attr])
+        (from == OPTION_NOT_GIVEN || from == attribute_was(attr))
     end
 
     # Handles <tt>*_was</tt> for +method_missing+.
     def attribute_was(attr) # :nodoc:
-      attribute_changed?(attr) ? changed_attributes[attr] : _read_attribute(attr)
+      mutations_from_database.original_value(attr)
     end
 
     # Handles <tt>*_previously_changed?</tt> for +method_missing+.
     def attribute_previously_changed?(attr) #:nodoc:
-      previous_changes_include?(attr)
+      mutations_before_last_save.changed?(attr)
     end
 
     # Restore all previous data of the provided attributes.
@@ -191,15 +191,12 @@ module ActiveModel
 
     # Clears all dirty data: current changes and previous changes.
     def clear_changes_information
-      @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
       @mutations_before_last_save = nil
-      @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
       forget_attribute_assignments
       @mutations_from_database = nil
     end
 
     def clear_attribute_changes(attr_names)
-      attributes_changed_by_setter.except!(*attr_names)
       attr_names.each do |attr_name|
         clear_attribute_change(attr_name)
       end
@@ -212,13 +209,7 @@ module ActiveModel
     #   person.name = 'robert'
     #   person.changed_attributes # => {"name" => "bob"}
     def changed_attributes
-      # This should only be set by methods which will call changed_attributes
-      # multiple times when it is known that the computed value cannot change.
-      if defined?(@cached_changed_attributes)
-        @cached_changed_attributes
-      else
-        attributes_changed_by_setter.reverse_merge(mutations_from_database.changed_values).freeze
-      end
+      mutations_from_database.changed_values.freeze
     end
 
     # Returns a hash of changed attributes indicating their original
@@ -228,9 +219,8 @@ module ActiveModel
     #   person.name = 'bob'
     #   person.changes # => { "name" => ["bill", "bob"] }
     def changes
-      cache_changed_attributes do
-        ActiveSupport::HashWithIndifferentAccess[changed.map { |attr| [attr, attribute_change(attr)] }]
-      end
+      _prepare_changes
+      mutations_from_database.changes
     end
 
     # Returns a hash of attributes that were changed before the model was saved.
@@ -240,8 +230,7 @@ module ActiveModel
     #   person.save
     #   person.previous_changes # => {"name" => ["bob", "robert"]}
     def previous_changes
-      @previously_changed ||= ActiveSupport::HashWithIndifferentAccess.new
-      @previously_changed.merge(mutations_before_last_save.changes)
+      mutations_before_last_save.changes
     end
 
     def attribute_changed_in_place?(attr_name) # :nodoc:
@@ -257,11 +246,17 @@ module ActiveModel
         unless defined?(@mutations_from_database)
           @mutations_from_database = nil
         end
-        @mutations_from_database ||= if defined?(@attributes)
-          ActiveModel::AttributeMutationTracker.new(@attributes)
-        else
-          NullMutationTracker.instance
+
+        unless defined?(@attributes)
+          @_pseudo_attributes = true
+          @attributes = AttributeSet.new(
+            Hash.new { |h, attr|
+              h[attr] = Attribute.with_cast_value(attr, _clone_attribute(attr), Type.default_value)
+            }
+          )
         end
+
+        @mutations_from_database ||= ActiveModel::AttributeMutationTracker.new(@attributes)
       end
 
       def forget_attribute_assignments
@@ -272,68 +267,45 @@ module ActiveModel
         @mutations_before_last_save ||= ActiveModel::NullMutationTracker.instance
       end
 
-      def cache_changed_attributes
-        @cached_changed_attributes = changed_attributes
-        yield
-      ensure
-        clear_changed_attributes_cache
-      end
-
-      def clear_changed_attributes_cache
-        remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
-      end
-
-      # Returns +true+ if attr_name is changed, +false+ otherwise.
-      def changes_include?(attr_name)
-        attributes_changed_by_setter.include?(attr_name) || mutations_from_database.changed?(attr_name)
-      end
-      alias attribute_changed_by_setter? changes_include?
-
-      # Returns +true+ if attr_name were changed before the model was saved,
-      # +false+ otherwise.
-      def previous_changes_include?(attr_name)
-        previous_changes.include?(attr_name)
-      end
-
       # Handles <tt>*_change</tt> for +method_missing+.
       def attribute_change(attr)
-        [changed_attributes[attr], _read_attribute(attr)] if attribute_changed?(attr)
+        [attribute_was(attr), _read_attribute(attr)] if attribute_changed?(attr)
       end
 
       # Handles <tt>*_previous_change</tt> for +method_missing+.
       def attribute_previous_change(attr)
-        previous_changes[attr] if attribute_previously_changed?(attr)
+        mutations_before_last_save.change_to_attribute(attr)
       end
 
       # Handles <tt>*_will_change!</tt> for +method_missing+.
       def attribute_will_change!(attr)
-        unless attribute_changed?(attr)
-          begin
-            value = _read_attribute(attr)
-            value = value.duplicable? ? value.clone : value
-          rescue TypeError, NoMethodError
-          end
-
-          set_attribute_was(attr, value)
+        attr = attr.to_s
+        mutations_from_database.force_change(attr).tap do
+          @attributes[attr] if defined?(@_pseudo_attributes)
         end
-        mutations_from_database.force_change(attr)
       end
 
       # Handles <tt>restore_*!</tt> for +method_missing+.
       def restore_attribute!(attr)
         if attribute_changed?(attr)
-          __send__("#{attr}=", changed_attributes[attr])
+          __send__("#{attr}=", attribute_was(attr))
           clear_attribute_changes([attr])
         end
       end
 
-      def attributes_changed_by_setter
-        @attributes_changed_by_setter ||= ActiveSupport::HashWithIndifferentAccess.new
+      def _prepare_changes
+        if defined?(@_pseudo_attributes)
+          changed.each do |attr|
+            @attributes.write_from_user(attr, _read_attribute(attr))
+          end
+        end
       end
 
-      # Force an attribute to have a particular "before" value
-      def set_attribute_was(attr, old_value)
-        attributes_changed_by_setter[attr] = old_value
+      def _clone_attribute(attr)
+        value = _read_attribute(attr)
+        value.duplicable? ? value.clone : value
+      rescue TypeError, NoMethodError
+        value
       end
   end
 end
diff --git a/activemodel/lib/active_model/gem_version.rb b/activemodel/lib/active_model/gem_version.rb
index 3c344fe854..cef5441e4a 100644
--- a/activemodel/lib/active_model/gem_version.rb
+++ b/activemodel/lib/active_model/gem_version.rb
@@ -7,10 +7,10 @@ module ActiveModel
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activemodel/lib/active_model/lint.rb b/activemodel/lib/active_model/lint.rb
index 34d9ac6c96..b7ceabb59a 100644
--- a/activemodel/lib/active_model/lint.rb
+++ b/activemodel/lib/active_model/lint.rb
@@ -29,7 +29,7 @@ module ActiveModel
       # <tt>to_key</tt> returns an Enumerable of all (primary) key attributes
       # of the model, and is used to a generate unique DOM id for the object.
       def test_to_key
-        assert model.respond_to?(:to_key), "The model should respond to to_key"
+        assert_respond_to model, :to_key
         def model.persisted?() false end
         assert model.to_key.nil?, "to_key should return nil when `persisted?` returns false"
       end
@@ -44,7 +44,7 @@ module ActiveModel
       # tests for this behavior in lint because it doesn't make sense to force
       # any of the possible implementation strategies on the implementer.
       def test_to_param
-        assert model.respond_to?(:to_param), "The model should respond to to_param"
+        assert_respond_to model, :to_param
         def model.to_key() [1] end
         def model.persisted?() false end
         assert model.to_param.nil?, "to_param should return nil when `persisted?` returns false"
@@ -56,7 +56,7 @@ module ActiveModel
       # <tt>to_partial_path</tt> is used for looking up partials. For example,
       # a BlogPost model might return "blog_posts/blog_post".
       def test_to_partial_path
-        assert model.respond_to?(:to_partial_path), "The model should respond to to_partial_path"
+        assert_respond_to model, :to_partial_path
         assert_kind_of String, model.to_partial_path
       end
 
@@ -68,7 +68,7 @@ module ActiveModel
       # will route to the create action. If it is persisted, a form for the
       # object will route to the update action.
       def test_persisted?
-        assert model.respond_to?(:persisted?), "The model should respond to persisted?"
+        assert_respond_to model, :persisted?
         assert_boolean model.persisted?, "persisted?"
       end
 
@@ -79,14 +79,14 @@ module ActiveModel
       #
       # Check ActiveModel::Naming for more information.
       def test_model_naming
-        assert model.class.respond_to?(:model_name), "The model class should respond to model_name"
+        assert_respond_to model.class, :model_name
         model_name = model.class.model_name
-        assert model_name.respond_to?(:to_str)
-        assert model_name.human.respond_to?(:to_str)
-        assert model_name.singular.respond_to?(:to_str)
-        assert model_name.plural.respond_to?(:to_str)
+        assert_respond_to model_name, :to_str
+        assert_respond_to model_name.human, :to_str
+        assert_respond_to model_name.singular, :to_str
+        assert_respond_to model_name.plural, :to_str
 
-        assert model.respond_to?(:model_name), "The model instance should respond to model_name"
+        assert_respond_to model, :model_name
         assert_equal model.model_name, model.class.model_name
       end
 
@@ -100,13 +100,13 @@ module ActiveModel
       # If localization is used, the strings should be localized for the current
       # locale. If no error is present, the method should return an empty array.
       def test_errors_aref
-        assert model.respond_to?(:errors), "The model should respond to errors"
+        assert_respond_to model, :errors
         assert model.errors[:hello].is_a?(Array), "errors#[] should return an Array"
       end
 
       private
         def model
-          assert @model.respond_to?(:to_model), "The object should respond to to_model"
+          assert_respond_to @model, :to_model
           @model.to_model
         end
 
diff --git a/activemodel/lib/active_model/type/date.rb b/activemodel/lib/active_model/type/date.rb
index 8cecc16d0f..8ec5deedc4 100644
--- a/activemodel/lib/active_model/type/date.rb
+++ b/activemodel/lib/active_model/type/date.rb
@@ -42,7 +42,7 @@ module ActiveModel
         end
 
         def new_date(year, mon, mday)
-          if year && year != 0
+          unless year.nil? || (year == 0 && mon == 0 && mday == 0)
             ::Date.new(year, mon, mday) rescue nil
           end
         end
diff --git a/activemodel/lib/active_model/type/integer.rb b/activemodel/lib/active_model/type/integer.rb
index fe396998a3..da74aaa3c5 100644
--- a/activemodel/lib/active_model/type/integer.rb
+++ b/activemodel/lib/active_model/type/integer.rb
@@ -31,13 +31,8 @@ module ActiveModel
         result
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :range
-
       private
+        attr_reader :range
 
         def cast_value(value)
           case value
diff --git a/activemodel/lib/active_model/type/registry.rb b/activemodel/lib/active_model/type/registry.rb
index 7272d7b0c5..a19dc0f011 100644
--- a/activemodel/lib/active_model/type/registry.rb
+++ b/activemodel/lib/active_model/type/registry.rb
@@ -23,13 +23,8 @@ module ActiveModel
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :registrations
-
       private
+        attr_reader :registrations
 
         def registration_klass
           Registration
@@ -59,10 +54,7 @@ module ActiveModel
         type_name == name
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :name, :block
     end
   end
diff --git a/activemodel/lib/active_model/validations/acceptance.rb b/activemodel/lib/active_model/validations/acceptance.rb
index f35e4dec7f..ea3a6b52ab 100644
--- a/activemodel/lib/active_model/validations/acceptance.rb
+++ b/activemodel/lib/active_model/validations/acceptance.rb
@@ -58,13 +58,8 @@ module ActiveModel
             klass.send(:attr_writer, *attr_writers)
           end
 
-          # TODO Change this to private once we've dropped Ruby 2.2 support.
-          # Workaround for Ruby 2.2 "private attribute?" warning.
-          protected
-
-            attr_reader :attributes
-
           private
+            attr_reader :attributes
 
             def convert_to_reader_name(method_name)
               method_name.to_s.chomp("=")
diff --git a/activemodel/lib/active_model/validations/clusivity.rb b/activemodel/lib/active_model/validations/clusivity.rb
index 0b9b5ce6a1..bafb8e2106 100644
--- a/activemodel/lib/active_model/validations/clusivity.rb
+++ b/activemodel/lib/active_model/validations/clusivity.rb
@@ -32,7 +32,7 @@ module ActiveModel
         @delimiter ||= options[:in] || options[:within]
       end
 
-      # In Ruby 2.2 <tt>Range#include?</tt> on non-number-or-time-ish ranges checks all
+      # After Ruby 2.2, <tt>Range#include?</tt> on non-number-or-time-ish ranges checks all
       # possible values in the range for equality, which is slower but more accurate.
       # <tt>Range#cover?</tt> uses the previous logic of comparing a value with the range
       # endpoints, which is fast but is only accurate on Numeric, Time, Date,
diff --git a/activemodel/test/cases/attribute_assignment_test.rb b/activemodel/test/cases/attribute_assignment_test.rb
index 5ecf0a69c4..448f8587fd 100644
--- a/activemodel/test/cases/attribute_assignment_test.rb
+++ b/activemodel/test/cases/attribute_assignment_test.rb
@@ -18,10 +18,7 @@ class AttributeAssignmentTest < ActiveModel::TestCase
       raise ErrorFromAttributeWriter
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
-
+    private
       attr_writer :metadata
   end
 
diff --git a/activemodel/test/cases/attribute_methods_test.rb b/activemodel/test/cases/attribute_methods_test.rb
index d2837ec894..0cfc6f4b6b 100644
--- a/activemodel/test/cases/attribute_methods_test.rb
+++ b/activemodel/test/cases/attribute_methods_test.rb
@@ -220,7 +220,7 @@ class AttributeMethodsTest < ActiveModel::TestCase
     ModelWithAttributes.define_attribute_methods(:foo)
     ModelWithAttributes.undefine_attribute_methods
 
-    assert !ModelWithAttributes.new.respond_to?(:foo)
+    assert_not_respond_to ModelWithAttributes.new, :foo
     assert_raises(NoMethodError) { ModelWithAttributes.new.foo }
   end
 
@@ -255,7 +255,7 @@ class AttributeMethodsTest < ActiveModel::TestCase
     m = ModelWithAttributes2.new
     m.attributes = { "private_method" => "<3", "protected_method" => "O_o" }
 
-    assert !m.respond_to?(:private_method)
+    assert_not_respond_to m, :private_method
     assert m.respond_to?(:private_method, true)
 
     c = ClassWithProtected.new
diff --git a/activemodel/test/cases/attribute_set_test.rb b/activemodel/test/cases/attribute_set_test.rb
index 6e522d6c80..b868dba743 100644
--- a/activemodel/test/cases/attribute_set_test.rb
+++ b/activemodel/test/cases/attribute_set_test.rb
@@ -74,8 +74,8 @@ module ActiveModel
 
       clone.freeze
 
-      assert clone.frozen?
-      assert_not attributes.frozen?
+      assert_predicate clone, :frozen?
+      assert_not_predicate attributes, :frozen?
     end
 
     test "to_hash returns a hash of the type cast values" do
@@ -105,8 +105,8 @@ module ActiveModel
 
     test "known columns are built with uninitialized attributes" do
       attributes = attributes_with_uninitialized_key
-      assert attributes[:foo].initialized?
-      assert_not attributes[:bar].initialized?
+      assert_predicate attributes[:foo], :initialized?
+      assert_not_predicate attributes[:bar], :initialized?
     end
 
     test "uninitialized attributes are not included in the attributes hash" do
@@ -169,7 +169,7 @@ module ActiveModel
 
       assert attributes.key?(:foo)
       assert_equal [:foo], attributes.keys
-      assert attributes[:foo].initialized?
+      assert_predicate attributes[:foo], :initialized?
     end
 
     class MyType
@@ -209,11 +209,6 @@ module ActiveModel
       assert_equal "value from user", attributes.fetch_value(:foo)
     end
 
-    def attributes_with_uninitialized_key
-      builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Float.new)
-      builder.build_from_database(foo: "1.1")
-    end
-
     test "freezing doesn't prevent the set from materializing" do
       builder = AttributeSet::Builder.new(foo: Type::String.new)
       attributes = builder.build_from_database(foo: "1")
@@ -222,6 +217,22 @@ module ActiveModel
       assert_equal({ foo: "1" }, attributes.to_hash)
     end
 
+    test "marshaling dump/load legacy materialized attribute hash" do
+      builder = AttributeSet::Builder.new(foo: Type::String.new)
+      attributes = builder.build_from_database(foo: "1")
+
+      attributes.instance_variable_get(:@attributes).instance_eval do
+        class << self
+          def marshal_dump
+            materialize
+          end
+        end
+      end
+
+      attributes = Marshal.load(Marshal.dump(attributes))
+      assert_equal({ foo: "1" }, attributes.to_hash)
+    end
+
     test "#accessed_attributes returns only attributes which have been read" do
       builder = AttributeSet::Builder.new(foo: Type::Value.new, bar: Type::Value.new)
       attributes = builder.build_from_database(foo: "1", bar: "2")
@@ -253,5 +264,11 @@ module ActiveModel
       assert_equal attributes, attributes2
       assert_not_equal attributes2, attributes3
     end
+
+    private
+      def attributes_with_uninitialized_key
+        builder = AttributeSet::Builder.new(foo: Type::Integer.new, bar: Type::Float.new)
+        builder.build_from_database(foo: "1.1")
+      end
   end
 end
diff --git a/activemodel/test/cases/attribute_test.rb b/activemodel/test/cases/attribute_test.rb
index 14d86cef97..ea2b0efd11 100644
--- a/activemodel/test/cases/attribute_test.rb
+++ b/activemodel/test/cases/attribute_test.rb
@@ -175,33 +175,33 @@ module ActiveModel
 
     test "an attribute has not been read by default" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
-      assert_not attribute.has_been_read?
+      assert_not_predicate attribute, :has_been_read?
     end
 
     test "an attribute has been read when its value is calculated" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
       attribute.value
-      assert attribute.has_been_read?
+      assert_predicate attribute, :has_been_read?
     end
 
     test "an attribute is not changed if it hasn't been assigned or mutated" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
 
-      refute attribute.changed?
+      assert_not_predicate attribute, :changed?
     end
 
     test "an attribute is changed if it's been assigned a new value" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
       changed = attribute.with_value_from_user(2)
 
-      assert changed.changed?
+      assert_predicate changed, :changed?
     end
 
     test "an attribute is not changed if it's assigned the same value" do
       attribute = Attribute.from_database(:foo, 1, Type::Value.new)
       unchanged = attribute.with_value_from_user(1)
 
-      refute unchanged.changed?
+      assert_not_predicate unchanged, :changed?
     end
 
     test "an attribute can not be mutated if it has not been read,
@@ -209,15 +209,15 @@ module ActiveModel
       type_which_raises_from_all_methods = Object.new
       attribute = Attribute.from_database(:foo, "bar", type_which_raises_from_all_methods)
 
-      assert_not attribute.changed_in_place?
+      assert_not_predicate attribute, :changed_in_place?
     end
 
     test "an attribute is changed if it has been mutated" do
       attribute = Attribute.from_database(:foo, "bar", Type::String.new)
       attribute.value << "!"
 
-      assert attribute.changed_in_place?
-      assert attribute.changed?
+      assert_predicate attribute, :changed_in_place?
+      assert_predicate attribute, :changed?
     end
 
     test "an attribute can forget its changes" do
@@ -226,7 +226,7 @@ module ActiveModel
       forgotten = changed.forgetting_assignment
 
       assert changed.changed? # sanity check
-      refute forgotten.changed?
+      assert_not_predicate forgotten, :changed?
     end
 
     test "with_value_from_user validates the value" do
diff --git a/activemodel/test/cases/attributes_dirty_test.rb b/activemodel/test/cases/attributes_dirty_test.rb
index 83a86371e0..c991176389 100644
--- a/activemodel/test/cases/attributes_dirty_test.rb
+++ b/activemodel/test/cases/attributes_dirty_test.rb
@@ -25,11 +25,11 @@ class AttributesDirtyTest < ActiveModel::TestCase
   end
 
   test "setting attribute will result in change" do
-    assert !@model.changed?
-    assert !@model.name_changed?
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
     @model.name = "Ringo"
-    assert @model.changed?
-    assert @model.name_changed?
+    assert_predicate @model, :changed?
+    assert_predicate @model, :name_changed?
   end
 
   test "list of changed attribute keys" do
@@ -71,35 +71,35 @@ class AttributesDirtyTest < ActiveModel::TestCase
   test "attribute mutation" do
     @model.name = "Yam"
     @model.save
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
     @model.name.replace("Hadad")
-    assert @model.name_changed?
+    assert_predicate @model, :name_changed?
   end
 
   test "resetting attribute" do
     @model.name = "Bob"
     @model.restore_name!
     assert_nil @model.name
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
   end
 
   test "setting color to same value should not result in change being recorded" do
     @model.color = "red"
-    assert @model.color_changed?
+    assert_predicate @model, :color_changed?
     @model.save
-    assert !@model.color_changed?
-    assert !@model.changed?
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
     @model.color = "red"
-    assert !@model.color_changed?
-    assert !@model.changed?
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
   end
 
   test "saving should reset model's changed status" do
     @model.name = "Alf"
-    assert @model.changed?
+    assert_predicate @model, :changed?
     @model.save
-    assert !@model.changed?
-    assert !@model.name_changed?
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
   end
 
   test "saving should preserve previous changes" do
@@ -118,7 +118,7 @@ class AttributesDirtyTest < ActiveModel::TestCase
   test "saving should preserve model's previous changed status" do
     @model.name = "Jericho Cane"
     @model.save
-    assert @model.name_previously_changed?
+    assert_predicate @model, :name_previously_changed?
   end
 
   test "previous value is preserved when changed after save" do
@@ -143,7 +143,7 @@ class AttributesDirtyTest < ActiveModel::TestCase
 
   test "using attribute_will_change! with a symbol" do
     @model.size = 1
-    assert @model.size_changed?
+    assert_predicate @model, :size_changed?
   end
 
   test "reload should reset all changes" do
@@ -170,7 +170,7 @@ class AttributesDirtyTest < ActiveModel::TestCase
 
     @model.restore_attributes
 
-    assert_not @model.changed?
+    assert_not_predicate @model, :changed?
     assert_equal "Dmitry", @model.name
     assert_equal "Red", @model.color
   end
@@ -184,7 +184,7 @@ class AttributesDirtyTest < ActiveModel::TestCase
 
     @model.restore_attributes(["name"])
 
-    assert @model.changed?
+    assert_predicate @model, :changed?
     assert_equal "Dmitry", @model.name
     assert_equal "White", @model.color
   end
diff --git a/activemodel/test/cases/attributes_test.rb b/activemodel/test/cases/attributes_test.rb
index e43bf15335..7c1d813ce0 100644
--- a/activemodel/test/cases/attributes_test.rb
+++ b/activemodel/test/cases/attributes_test.rb
@@ -64,5 +64,14 @@ module ActiveModel
 
       assert_equal "4.4", data.integer_field
     end
+
+    test "attributes with proc defaults can be marshalled" do
+      data = ModelForAttributesTest.new
+      attributes = data.instance_variable_get(:@attributes)
+      round_tripped = Marshal.load(Marshal.dump(data))
+      new_attributes = round_tripped.instance_variable_get(:@attributes)
+
+      assert_equal attributes, new_attributes
+    end
   end
 end
diff --git a/activemodel/test/cases/callbacks_test.rb b/activemodel/test/cases/callbacks_test.rb
index a5d29d0f22..1ec12d8222 100644
--- a/activemodel/test/cases/callbacks_test.rb
+++ b/activemodel/test/cases/callbacks_test.rb
@@ -85,21 +85,21 @@ class CallbacksTest < ActiveModel::TestCase
   end
 
   test "only selects which types of callbacks should be created" do
-    assert !ModelCallbacks.respond_to?(:before_initialize)
-    assert !ModelCallbacks.respond_to?(:around_initialize)
+    assert_not_respond_to ModelCallbacks, :before_initialize
+    assert_not_respond_to ModelCallbacks, :around_initialize
     assert_respond_to ModelCallbacks, :after_initialize
   end
 
   test "only selects which types of callbacks should be created from an array list" do
     assert_respond_to ModelCallbacks, :before_multiple
     assert_respond_to ModelCallbacks, :around_multiple
-    assert !ModelCallbacks.respond_to?(:after_multiple)
+    assert_not_respond_to ModelCallbacks, :after_multiple
   end
 
   test "no callbacks should be created" do
-    assert !ModelCallbacks.respond_to?(:before_empty)
-    assert !ModelCallbacks.respond_to?(:around_empty)
-    assert !ModelCallbacks.respond_to?(:after_empty)
+    assert_not_respond_to ModelCallbacks, :before_empty
+    assert_not_respond_to ModelCallbacks, :around_empty
+    assert_not_respond_to ModelCallbacks, :after_empty
   end
 
   class Violin
diff --git a/activemodel/test/cases/dirty_test.rb b/activemodel/test/cases/dirty_test.rb
index dfe041ff50..f769eb0da1 100644
--- a/activemodel/test/cases/dirty_test.rb
+++ b/activemodel/test/cases/dirty_test.rb
@@ -5,12 +5,13 @@ require "cases/helper"
 class DirtyTest < ActiveModel::TestCase
   class DirtyModel
     include ActiveModel::Dirty
-    define_attribute_methods :name, :color, :size
+    define_attribute_methods :name, :color, :size, :status
 
     def initialize
       @name = nil
       @color = nil
       @size = nil
+      @status = "initialized"
     end
 
     def name
@@ -40,6 +41,15 @@ class DirtyTest < ActiveModel::TestCase
       @size = val
     end
 
+    def status
+      @status
+    end
+
+    def status=(val)
+      status_will_change! unless val == @status
+      @status = val
+    end
+
     def save
       changes_applied
     end
@@ -54,11 +64,11 @@ class DirtyTest < ActiveModel::TestCase
   end
 
   test "setting attribute will result in change" do
-    assert !@model.changed?
-    assert !@model.name_changed?
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
     @model.name = "Ringo"
-    assert @model.changed?
-    assert @model.name_changed?
+    assert_predicate @model, :changed?
+    assert_predicate @model, :name_changed?
   end
 
   test "list of changed attribute keys" do
@@ -99,82 +109,93 @@ class DirtyTest < ActiveModel::TestCase
 
   test "attribute mutation" do
     @model.instance_variable_set("@name", "Yam".dup)
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
     @model.name.replace("Hadad")
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
     @model.name_will_change!
     @model.name.replace("Baal")
-    assert @model.name_changed?
+    assert_predicate @model, :name_changed?
   end
 
   test "resetting attribute" do
     @model.name = "Bob"
     @model.restore_name!
     assert_nil @model.name
-    assert !@model.name_changed?
+    assert_not_predicate @model, :name_changed?
   end
 
   test "setting color to same value should not result in change being recorded" do
     @model.color = "red"
-    assert @model.color_changed?
+    assert_predicate @model, :color_changed?
     @model.save
-    assert !@model.color_changed?
-    assert !@model.changed?
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
     @model.color = "red"
-    assert !@model.color_changed?
-    assert !@model.changed?
+    assert_not_predicate @model, :color_changed?
+    assert_not_predicate @model, :changed?
   end
 
   test "saving should reset model's changed status" do
     @model.name = "Alf"
-    assert @model.changed?
+    assert_predicate @model, :changed?
     @model.save
-    assert !@model.changed?
-    assert !@model.name_changed?
+    assert_not_predicate @model, :changed?
+    assert_not_predicate @model, :name_changed?
   end
 
   test "saving should preserve previous changes" do
     @model.name = "Jericho Cane"
+    @model.status = "waiting"
     @model.save
     assert_equal [nil, "Jericho Cane"], @model.previous_changes["name"]
+    assert_equal ["initialized", "waiting"], @model.previous_changes["status"]
   end
 
   test "setting new attributes should not affect previous changes" do
     @model.name = "Jericho Cane"
+    @model.status = "waiting"
     @model.save
     @model.name = "DudeFella ManGuy"
+    @model.status = "finished"
     assert_equal [nil, "Jericho Cane"], @model.name_previous_change
+    assert_equal ["initialized", "waiting"], @model.previous_changes["status"]
   end
 
   test "saving should preserve model's previous changed status" do
     @model.name = "Jericho Cane"
     @model.save
-    assert @model.name_previously_changed?
+    assert_predicate @model, :name_previously_changed?
   end
 
   test "previous value is preserved when changed after save" do
     assert_equal({}, @model.changed_attributes)
     @model.name = "Paul"
-    assert_equal({ "name" => nil }, @model.changed_attributes)
+    @model.status = "waiting"
+    assert_equal({ "name" => nil, "status" => "initialized" }, @model.changed_attributes)
 
     @model.save
 
     @model.name = "John"
-    assert_equal({ "name" => "Paul" }, @model.changed_attributes)
+    @model.status = "finished"
+    assert_equal({ "name" => "Paul", "status" => "waiting" }, @model.changed_attributes)
   end
 
   test "changing the same attribute multiple times retains the correct original value" do
     @model.name = "Otto"
+    @model.status = "waiting"
     @model.save
     @model.name = "DudeFella ManGuy"
     @model.name = "Mr. Manfredgensonton"
+    @model.status = "processing"
+    @model.status = "finished"
     assert_equal ["Otto", "Mr. Manfredgensonton"], @model.name_change
+    assert_equal ["waiting", "finished"], @model.status_change
     assert_equal @model.name_was, "Otto"
   end
 
   test "using attribute_will_change! with a symbol" do
     @model.size = 1
-    assert @model.size_changed?
+    assert_predicate @model, :size_changed?
   end
 
   test "reload should reset all changes" do
@@ -201,7 +222,7 @@ class DirtyTest < ActiveModel::TestCase
 
     @model.restore_attributes
 
-    assert_not @model.changed?
+    assert_not_predicate @model, :changed?
     assert_equal "Dmitry", @model.name
     assert_equal "Red", @model.color
   end
@@ -215,7 +236,7 @@ class DirtyTest < ActiveModel::TestCase
 
     @model.restore_attributes(["name"])
 
-    assert @model.changed?
+    assert_predicate @model, :changed?
     assert_equal "Dmitry", @model.name
     assert_equal "White", @model.color
   end
diff --git a/activemodel/test/cases/errors_test.rb b/activemodel/test/cases/errors_test.rb
index d5c282b620..cb6a8c43d5 100644
--- a/activemodel/test/cases/errors_test.rb
+++ b/activemodel/test/cases/errors_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "cases/helper"
-require "active_support/core_ext/string/strip"
 require "yaml"
 
 class ErrorsTest < ActiveModel::TestCase
@@ -83,7 +82,7 @@ class ErrorsTest < ActiveModel::TestCase
 
     assert_equal 1, person.errors.count
     person.errors.clear
-    assert person.errors.empty?
+    assert_empty person.errors
   end
 
   test "error access is indifferent" do
@@ -128,8 +127,8 @@ class ErrorsTest < ActiveModel::TestCase
   test "detecting whether there are errors with empty?, blank?, include?" do
     person = Person.new
     person.errors[:foo]
-    assert person.errors.empty?
-    assert person.errors.blank?
+    assert_empty person.errors
+    assert_predicate person.errors, :blank?
     assert_not_includes person.errors, :foo
   end
 
@@ -320,7 +319,7 @@ class ErrorsTest < ActiveModel::TestCase
 
   test "generate_message works without i18n_scope" do
     person = Person.new
-    assert !Person.respond_to?(:i18n_scope)
+    assert_not_respond_to Person, :i18n_scope
     assert_nothing_raised {
       person.errors.generate_message(:name, :blank)
     }
@@ -371,7 +370,7 @@ class ErrorsTest < ActiveModel::TestCase
 
     assert_equal 1, person.errors.details.count
     person.errors.clear
-    assert person.errors.details.empty?
+    assert_empty person.errors.details
   end
 
   test "copy errors" do
@@ -406,7 +405,7 @@ class ErrorsTest < ActiveModel::TestCase
   end
 
   test "errors are backward compatible with the Rails 4.2 format" do
-    yaml = <<-CODE.strip_heredoc
+    yaml = <<~CODE
     --- !ruby/object:ActiveModel::Errors
     base: &1 !ruby/object:ErrorsTest::Person
       errors: !ruby/object:ActiveModel::Errors
diff --git a/activemodel/test/cases/type/boolean_test.rb b/activemodel/test/cases/type/boolean_test.rb
index 2d33579595..2de0f53640 100644
--- a/activemodel/test/cases/type/boolean_test.rb
+++ b/activemodel/test/cases/type/boolean_test.rb
@@ -7,8 +7,8 @@ module ActiveModel
     class BooleanTest < ActiveModel::TestCase
       def test_type_cast_boolean
         type = Type::Boolean.new
-        assert type.cast("").nil?
-        assert type.cast(nil).nil?
+        assert_predicate type.cast(""), :nil?
+        assert_predicate type.cast(nil), :nil?
 
         assert type.cast(true)
         assert type.cast(1)
diff --git a/activemodel/test/cases/validations/absence_validation_test.rb b/activemodel/test/cases/validations/absence_validation_test.rb
index 801577474a..8bc4f4723a 100644
--- a/activemodel/test/cases/validations/absence_validation_test.rb
+++ b/activemodel/test/cases/validations/absence_validation_test.rb
@@ -17,16 +17,16 @@ class AbsenceValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "foo"
     t.content = "bar"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be blank"], t.errors[:title]
     assert_equal ["must be blank"], t.errors[:content]
     t.title = ""
     t.content = "something"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be blank"], t.errors[:content]
     assert_equal [], t.errors[:title]
     t.content = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_absence_of_with_array_arguments
@@ -34,7 +34,7 @@ class AbsenceValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "foo"
     t.content = "bar"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be blank"], t.errors[:title]
     assert_equal ["must be blank"], t.errors[:content]
   end
@@ -43,7 +43,7 @@ class AbsenceValidationTest < ActiveModel::TestCase
     Person.validates_absence_of :karma, message: "This string contains 'single' and \"double\" quotes"
     p = Person.new
     p.karma = "good"
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal "This string contains 'single' and \"double\" quotes", p.errors[:karma].last
   end
 
@@ -51,19 +51,19 @@ class AbsenceValidationTest < ActiveModel::TestCase
     Person.validates_absence_of :karma
     p = Person.new
     p.karma = "good"
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["must be blank"], p.errors[:karma]
     p.karma = nil
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 
   def test_validates_absence_of_for_ruby_class_with_custom_reader
     CustomReader.validates_absence_of :karma
     p = CustomReader.new
     p[:karma] = "excellent"
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["must be blank"], p.errors[:karma]
     p[:karma] = ""
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/acceptance_validation_test.rb b/activemodel/test/cases/validations/acceptance_validation_test.rb
index c5f54b1868..7662f996ae 100644
--- a/activemodel/test/cases/validations/acceptance_validation_test.rb
+++ b/activemodel/test/cases/validations/acceptance_validation_test.rb
@@ -15,54 +15,54 @@ class AcceptanceValidationTest < ActiveModel::TestCase
     Topic.validates_acceptance_of(:terms_of_service)
 
     t = Topic.new("title" => "We should not be confirmed")
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_terms_of_service_agreement
     Topic.validates_acceptance_of(:terms_of_service)
 
     t = Topic.new("title" => "We should be confirmed", "terms_of_service" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = "1"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_eula
     Topic.validates_acceptance_of(:eula, message: "must be abided")
 
     t = Topic.new("title" => "We should be confirmed", "eula" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be abided"], t.errors[:eula]
 
     t.eula = "1"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_terms_of_service_agreement_with_accept_value
     Topic.validates_acceptance_of(:terms_of_service, accept: "I agree.")
 
     t = Topic.new("title" => "We should be confirmed", "terms_of_service" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = "I agree."
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_terms_of_service_agreement_with_multiple_accept_values
     Topic.validates_acceptance_of(:terms_of_service, accept: [1, "I concur."])
 
     t = Topic.new("title" => "We should be confirmed", "terms_of_service" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["must be accepted"], t.errors[:terms_of_service]
 
     t.terms_of_service = 1
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.terms_of_service = "I concur."
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_acceptance_of_for_ruby_class
@@ -71,11 +71,11 @@ class AcceptanceValidationTest < ActiveModel::TestCase
     p = Person.new
     p.karma = ""
 
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["must be accepted"], p.errors[:karma]
 
     p.karma = "1"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -83,6 +83,6 @@ class AcceptanceValidationTest < ActiveModel::TestCase
   def test_validates_acceptance_of_true
     Topic.validates_acceptance_of(:terms_of_service)
 
-    assert Topic.new(terms_of_service: true).valid?
+    assert_predicate Topic.new(terms_of_service: true), :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/conditional_validation_test.rb b/activemodel/test/cases/validations/conditional_validation_test.rb
index caea8b65ef..1704db9a48 100644
--- a/activemodel/test/cases/validations/conditional_validation_test.rb
+++ b/activemodel/test/cases/validations/conditional_validation_test.rb
@@ -13,24 +13,24 @@ class ConditionalValidationTest < ActiveModel::TestCase
     # When the method returns true
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_if_validation_using_array_of_true_methods
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: [:condition_is_true, :condition_is_true])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_unless_validation_using_array_of_false_methods
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: [:condition_is_false, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -38,21 +38,21 @@ class ConditionalValidationTest < ActiveModel::TestCase
     # When the method returns true
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_true)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
   def test_if_validation_using_array_of_true_and_false_methods
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: [:condition_is_true, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
   def test_unless_validation_using_array_of_true_and_felse_methods
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: [:condition_is_true, :condition_is_false])
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
@@ -60,7 +60,7 @@ class ConditionalValidationTest < ActiveModel::TestCase
     # When the method returns false
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
@@ -68,8 +68,8 @@ class ConditionalValidationTest < ActiveModel::TestCase
     # When the method returns false
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", unless: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -78,8 +78,8 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       if: Proc.new { |r| r.content.size > 4 })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -88,7 +88,7 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       unless: Proc.new { |r| r.content.size > 4 })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
@@ -97,7 +97,7 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       if: Proc.new { |r| r.title != "uhohuhoh" })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
@@ -106,23 +106,23 @@ class ConditionalValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}",
       unless: Proc.new { |r| r.title != "uhohuhoh" })
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
   def test_validation_using_conbining_if_true_and_unless_true_conditions
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true, unless: :condition_is_true)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
     assert_empty t.errors[:title]
   end
 
   def test_validation_using_conbining_if_true_and_unless_false_conditions
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}", if: :condition_is_true, unless: :condition_is_false)
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 end
diff --git a/activemodel/test/cases/validations/confirmation_validation_test.rb b/activemodel/test/cases/validations/confirmation_validation_test.rb
index 8b2c65289b..8603a8ac5c 100644
--- a/activemodel/test/cases/validations/confirmation_validation_test.rb
+++ b/activemodel/test/cases/validations/confirmation_validation_test.rb
@@ -14,40 +14,40 @@ class ConfirmationValidationTest < ActiveModel::TestCase
     Topic.validates_confirmation_of(:title)
 
     t = Topic.new(author_name: "Plutarch")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title_confirmation = "Parallel Lives"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title_confirmation = nil
     t.title = "Parallel Lives"
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title_confirmation = "Parallel Lives"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_title_confirmation
     Topic.validates_confirmation_of(:title)
 
     t = Topic.new("title" => "We should be confirmed", "title_confirmation" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title_confirmation = "We should be confirmed"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_confirmation_of_with_boolean_attribute
     Topic.validates_confirmation_of(:approved)
 
     t = Topic.new(approved: true, approved_confirmation: nil)
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.approved_confirmation = false
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.approved_confirmation = true
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_confirmation_of_for_ruby_class
@@ -55,12 +55,12 @@ class ConfirmationValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma_confirmation = "None"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["doesn't match Karma"], p.errors[:karma_confirmation]
 
     p.karma = "None"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -77,7 +77,7 @@ class ConfirmationValidationTest < ActiveModel::TestCase
       Topic.validates_confirmation_of(:title)
 
       t = Topic.new("title" => "We should be confirmed", "title_confirmation" => "")
-      assert t.invalid?
+      assert_predicate t, :invalid?
       assert_equal ["doesn't match Test Title"], t.errors[:title_confirmation]
     ensure
       I18n.load_path.replace @old_load_path
@@ -122,13 +122,13 @@ class ConfirmationValidationTest < ActiveModel::TestCase
     Topic.validates_confirmation_of(:title, case_sensitive: true)
 
     t = Topic.new(title: "title", title_confirmation: "Title")
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_title_confirmation_with_case_sensitive_option_false
     Topic.validates_confirmation_of(:title, case_sensitive: false)
 
     t = Topic.new(title: "title", title_confirmation: "Title")
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/exclusion_validation_test.rb b/activemodel/test/cases/validations/exclusion_validation_test.rb
index 68d611e904..50bd47065c 100644
--- a/activemodel/test/cases/validations/exclusion_validation_test.rb
+++ b/activemodel/test/cases/validations/exclusion_validation_test.rb
@@ -14,8 +14,8 @@ class ExclusionValidationTest < ActiveModel::TestCase
   def test_validates_exclusion_of
     Topic.validates_exclusion_of(:title, in: %w( abe monkey ))
 
-    assert Topic.new("title" => "something", "content" => "abc").valid?
-    assert Topic.new("title" => "monkey", "content" => "abc").invalid?
+    assert_predicate Topic.new("title" => "something", "content" => "abc"), :valid?
+    assert_predicate Topic.new("title" => "monkey", "content" => "abc"), :invalid?
   end
 
   def test_validates_exclusion_of_with_formatted_message
@@ -24,8 +24,8 @@ class ExclusionValidationTest < ActiveModel::TestCase
     assert Topic.new("title" => "something", "content" => "abc")
 
     t = Topic.new("title" => "monkey")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["option monkey is restricted"], t.errors[:title]
   end
 
@@ -35,8 +35,8 @@ class ExclusionValidationTest < ActiveModel::TestCase
     assert Topic.new("title" => "something", "content" => "abc")
 
     t = Topic.new("title" => "monkey")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
   end
 
   def test_validates_exclusion_of_for_ruby_class
@@ -44,12 +44,12 @@ class ExclusionValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "abe"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is reserved"], p.errors[:karma]
 
     p.karma = "Lifo"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -60,26 +60,26 @@ class ExclusionValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "elephant"
     t.author_name = "sikachu"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = "wasabi"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_exclusion_of_with_range
     Topic.validates_exclusion_of :content, in: ("a".."g")
 
-    assert Topic.new(content: "g").invalid?
-    assert Topic.new(content: "h").valid?
+    assert_predicate Topic.new(content: "g"), :invalid?
+    assert_predicate Topic.new(content: "h"), :valid?
   end
 
   def test_validates_exclusion_of_with_time_range
     Topic.validates_exclusion_of :created_at, in: 6.days.ago..2.days.ago
 
-    assert Topic.new(created_at: 5.days.ago).invalid?
-    assert Topic.new(created_at: 3.days.ago).invalid?
-    assert Topic.new(created_at: 7.days.ago).valid?
-    assert Topic.new(created_at: 1.day.ago).valid?
+    assert_predicate Topic.new(created_at: 5.days.ago), :invalid?
+    assert_predicate Topic.new(created_at: 3.days.ago), :invalid?
+    assert_predicate Topic.new(created_at: 7.days.ago), :valid?
+    assert_predicate Topic.new(created_at: 1.day.ago), :valid?
   end
 
   def test_validates_inclusion_of_with_symbol
@@ -92,7 +92,7 @@ class ExclusionValidationTest < ActiveModel::TestCase
       %w(abe)
     end
 
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["is reserved"], p.errors[:karma]
 
     p = Person.new
@@ -102,7 +102,7 @@ class ExclusionValidationTest < ActiveModel::TestCase
       %w()
     end
 
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
diff --git a/activemodel/test/cases/validations/format_validation_test.rb b/activemodel/test/cases/validations/format_validation_test.rb
index b0de80a6fc..2a7088b3e8 100644
--- a/activemodel/test/cases/validations/format_validation_test.rb
+++ b/activemodel/test/cases/validations/format_validation_test.rb
@@ -16,22 +16,22 @@ class FormatValidationTest < ActiveModel::TestCase
     t = Topic.new("title" => "i'm incorrect", "content" => "Validation macros rule!")
     assert t.invalid?, "Shouldn't be valid"
     assert_equal ["is bad data"], t.errors[:title]
-    assert t.errors[:content].empty?
+    assert_empty t.errors[:content]
 
     t.title = "Validation macros rule!"
 
-    assert t.valid?
-    assert t.errors[:title].empty?
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
 
     assert_raise(ArgumentError) { Topic.validates_format_of(:title, :content) }
   end
 
   def test_validate_format_with_allow_blank
     Topic.validates_format_of(:title, with: /\AValidation\smacros \w+!\z/, allow_blank: true)
-    assert Topic.new("title" => "Shouldn't be valid").invalid?
-    assert Topic.new("title" => "").valid?
-    assert Topic.new("title" => nil).valid?
-    assert Topic.new("title" => "Validation macros rule!").valid?
+    assert_predicate Topic.new("title" => "Shouldn't be valid"), :invalid?
+    assert_predicate Topic.new("title" => ""), :valid?
+    assert_predicate Topic.new("title" => nil), :valid?
+    assert_predicate Topic.new("title" => "Validation macros rule!"), :valid?
   end
 
   # testing ticket #3142
@@ -42,7 +42,7 @@ class FormatValidationTest < ActiveModel::TestCase
     assert t.invalid?, "Shouldn't be valid"
 
     assert_equal ["is bad data"], t.errors[:title]
-    assert t.errors[:content].empty?
+    assert_empty t.errors[:content]
 
     t.title = "-11"
     assert t.invalid?, "Shouldn't be valid"
@@ -58,14 +58,14 @@ class FormatValidationTest < ActiveModel::TestCase
 
     t.title = "1"
 
-    assert t.valid?
-    assert t.errors[:title].empty?
+    assert_predicate t, :valid?
+    assert_empty t.errors[:title]
   end
 
   def test_validate_format_with_formatted_message
     Topic.validates_format_of(:title, with: /\AValid Title\z/, message: "can't be %{value}")
     t = Topic.new(title: "Invalid title")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be Invalid title"], t.errors[:title]
   end
 
@@ -114,10 +114,10 @@ class FormatValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "digit"
     t.content = "Pixies"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.content = "1234"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_format_of_without_lambda
@@ -126,10 +126,10 @@ class FormatValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "characters"
     t.content = "1234"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.content = "Pixies"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_format_of_for_ruby_class
@@ -137,12 +137,12 @@ class FormatValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Pixies"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is invalid"], p.errors[:karma]
 
     p.karma = "1234"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
diff --git a/activemodel/test/cases/validations/inclusion_validation_test.rb b/activemodel/test/cases/validations/inclusion_validation_test.rb
index 94df0649a9..daad76759f 100644
--- a/activemodel/test/cases/validations/inclusion_validation_test.rb
+++ b/activemodel/test/cases/validations/inclusion_validation_test.rb
@@ -13,61 +13,61 @@ class InclusionValidationTest < ActiveModel::TestCase
 
   def test_validates_inclusion_of_range
     Topic.validates_inclusion_of(:title, in: "aaa".."bbb")
-    assert Topic.new("title" => "bbc", "content" => "abc").invalid?
-    assert Topic.new("title" => "aa", "content" => "abc").invalid?
-    assert Topic.new("title" => "aaab", "content" => "abc").invalid?
-    assert Topic.new("title" => "aaa", "content" => "abc").valid?
-    assert Topic.new("title" => "abc", "content" => "abc").valid?
-    assert Topic.new("title" => "bbb", "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "bbc", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "aa", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "aaab", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "aaa", "content" => "abc"), :valid?
+    assert_predicate Topic.new("title" => "abc", "content" => "abc"), :valid?
+    assert_predicate Topic.new("title" => "bbb", "content" => "abc"), :valid?
   end
 
   def test_validates_inclusion_of_time_range
     range_begin = 1.year.ago
     range_end = Time.now
     Topic.validates_inclusion_of(:created_at, in: range_begin..range_end)
-    assert Topic.new(title: "aaa", created_at: 2.years.ago).invalid?
-    assert Topic.new(title: "aaa", created_at: 3.months.ago).valid?
-    assert Topic.new(title: "aaa", created_at: 37.weeks.from_now).invalid?
-    assert Topic.new(title: "aaa", created_at: range_begin).valid?
-    assert Topic.new(title: "aaa", created_at: range_end).valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 2.years.ago), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 3.months.ago), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 37.weeks.from_now), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_begin), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_end), :valid?
   end
 
   def test_validates_inclusion_of_date_range
     range_begin = 1.year.until(Date.today)
     range_end = Date.today
     Topic.validates_inclusion_of(:created_at, in: range_begin..range_end)
-    assert Topic.new(title: "aaa", created_at: 2.years.until(Date.today)).invalid?
-    assert Topic.new(title: "aaa", created_at: 3.months.until(Date.today)).valid?
-    assert Topic.new(title: "aaa", created_at: 37.weeks.since(Date.today)).invalid?
-    assert Topic.new(title: "aaa", created_at: 1.year.until(Date.today)).valid?
-    assert Topic.new(title: "aaa", created_at: Date.today).valid?
-    assert Topic.new(title: "aaa", created_at: range_begin).valid?
-    assert Topic.new(title: "aaa", created_at: range_end).valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 2.years.until(Date.today)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 3.months.until(Date.today)), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 37.weeks.since(Date.today)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 1.year.until(Date.today)), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: Date.today), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_begin), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_end), :valid?
   end
 
   def test_validates_inclusion_of_date_time_range
     range_begin = 1.year.until(DateTime.current)
     range_end = DateTime.current
     Topic.validates_inclusion_of(:created_at, in: range_begin..range_end)
-    assert Topic.new(title: "aaa", created_at: 2.years.until(DateTime.current)).invalid?
-    assert Topic.new(title: "aaa", created_at: 3.months.until(DateTime.current)).valid?
-    assert Topic.new(title: "aaa", created_at: 37.weeks.since(DateTime.current)).invalid?
-    assert Topic.new(title: "aaa", created_at: range_begin).valid?
-    assert Topic.new(title: "aaa", created_at: range_end).valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 2.years.until(DateTime.current)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: 3.months.until(DateTime.current)), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: 37.weeks.since(DateTime.current)), :invalid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_begin), :valid?
+    assert_predicate Topic.new(title: "aaa", created_at: range_end), :valid?
   end
 
   def test_validates_inclusion_of
     Topic.validates_inclusion_of(:title, in: %w( a b c d e f g ))
 
-    assert Topic.new("title" => "a!", "content" => "abc").invalid?
-    assert Topic.new("title" => "a b", "content" => "abc").invalid?
-    assert Topic.new("title" => nil, "content" => "def").invalid?
+    assert_predicate Topic.new("title" => "a!", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "a b", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => nil, "content" => "def"), :invalid?
 
     t = Topic.new("title" => "a", "content" => "I know you are but what am I?")
-    assert t.valid?
+    assert_predicate t, :valid?
     t.title = "uhoh"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is not included in the list"], t.errors[:title]
 
     assert_raise(ArgumentError) { Topic.validates_inclusion_of(:title, in: nil) }
@@ -81,30 +81,30 @@ class InclusionValidationTest < ActiveModel::TestCase
   def test_validates_inclusion_of_with_allow_nil
     Topic.validates_inclusion_of(:title, in: %w( a b c d e f g ), allow_nil: true)
 
-    assert Topic.new("title" => "a!", "content" => "abc").invalid?
-    assert Topic.new("title" => "",   "content" => "abc").invalid?
-    assert Topic.new("title" => nil,  "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "a!", "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => "",   "content" => "abc"), :invalid?
+    assert_predicate Topic.new("title" => nil,  "content" => "abc"), :valid?
   end
 
   def test_validates_inclusion_of_with_formatted_message
     Topic.validates_inclusion_of(:title, in: %w( a b c d e f g ), message: "option %{value} is not in the list")
 
-    assert Topic.new("title" => "a", "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "a", "content" => "abc"), :valid?
 
     t = Topic.new("title" => "uhoh", "content" => "abc")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["option uhoh is not in the list"], t.errors[:title]
   end
 
   def test_validates_inclusion_of_with_within_option
     Topic.validates_inclusion_of(:title, within: %w( a b c d e f g ))
 
-    assert Topic.new("title" => "a", "content" => "abc").valid?
+    assert_predicate Topic.new("title" => "a", "content" => "abc"), :valid?
 
     t = Topic.new("title" => "uhoh", "content" => "abc")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
   end
 
   def test_validates_inclusion_of_for_ruby_class
@@ -112,12 +112,12 @@ class InclusionValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Lifo"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is not included in the list"], p.errors[:karma]
 
     p.karma = "monkey"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -128,10 +128,10 @@ class InclusionValidationTest < ActiveModel::TestCase
     t = Topic.new
     t.title = "wasabi"
     t.author_name = "sikachu"
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = "elephant"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_inclusion_of_with_symbol
@@ -144,7 +144,7 @@ class InclusionValidationTest < ActiveModel::TestCase
       %w()
     end
 
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal ["is not included in the list"], p.errors[:karma]
 
     p = Person.new
@@ -154,7 +154,7 @@ class InclusionValidationTest < ActiveModel::TestCase
       %w(Lifo)
     end
 
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
diff --git a/activemodel/test/cases/validations/length_validation_test.rb b/activemodel/test/cases/validations/length_validation_test.rb
index 42f76f3e3c..774a2cde74 100644
--- a/activemodel/test/cases/validations/length_validation_test.rb
+++ b/activemodel/test/cases/validations/length_validation_test.rb
@@ -13,153 +13,153 @@ class LengthValidationTest < ActiveModel::TestCase
   def test_validates_length_of_with_allow_nil
     Topic.validates_length_of(:title, is: 5, allow_nil: true)
 
-    assert Topic.new("title" => "ab").invalid?
-    assert Topic.new("title" => "").invalid?
-    assert Topic.new("title" => nil).valid?
-    assert Topic.new("title" => "abcde").valid?
+    assert_predicate Topic.new("title" => "ab"), :invalid?
+    assert_predicate Topic.new("title" => ""), :invalid?
+    assert_predicate Topic.new("title" => nil), :valid?
+    assert_predicate Topic.new("title" => "abcde"), :valid?
   end
 
   def test_validates_length_of_with_allow_blank
     Topic.validates_length_of(:title, is: 5, allow_blank: true)
 
-    assert Topic.new("title" => "ab").invalid?
-    assert Topic.new("title" => "").valid?
-    assert Topic.new("title" => nil).valid?
-    assert Topic.new("title" => "abcde").valid?
+    assert_predicate Topic.new("title" => "ab"), :invalid?
+    assert_predicate Topic.new("title" => ""), :valid?
+    assert_predicate Topic.new("title" => nil), :valid?
+    assert_predicate Topic.new("title" => "abcde"), :valid?
   end
 
   def test_validates_length_of_using_minimum
     Topic.validates_length_of :title, minimum: 5
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "not"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors[:title]
 
     t.title = nil
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors["title"]
   end
 
   def test_validates_length_of_using_maximum_should_allow_nil
     Topic.validates_length_of :title, maximum: 10
     t = Topic.new
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_minimum
     Topic.validates_length_of :title, minimum: 5, allow_nil: true
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_maximum
     Topic.validates_length_of :title, maximum: 5
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "notvalid"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_maximum
     Topic.validates_length_of :title, maximum: 5, allow_nil: true
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_within
     Topic.validates_length_of(:title, :content, within: 3..5)
 
     t = Topic.new("title" => "a!", "content" => "I'm ooooooooh so very long")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:content]
 
     t.title = nil
     t.content = nil
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:content]
 
     t.title = "abe"
     t.content = "mad"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_within_with_exclusive_range
     Topic.validates_length_of(:title, within: 4...10)
 
     t = Topic.new("title" => "9 chars!!")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "Now I'm 10"
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too long (maximum is 9 characters)"], t.errors[:title]
 
     t.title = "Four"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_within
     Topic.validates_length_of :title, :content, within: 3..5, allow_nil: true
 
     t = Topic.new("title" => "abc", "content" => "abcd")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_is
     Topic.validates_length_of :title, is: 5
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "notvalid"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is the wrong length (should be 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = nil
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_optionally_validates_length_of_using_is
     Topic.validates_length_of :title, is: 5, allow_nil: true
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = nil
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_bignum
@@ -187,45 +187,45 @@ class LengthValidationTest < ActiveModel::TestCase
   def test_validates_length_of_custom_errors_for_minimum_with_message
     Topic.validates_length_of(:title, minimum: 5, message: "boo %{count}")
     t = Topic.new("title" => "uhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["boo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_minimum_with_too_short
     Topic.validates_length_of(:title, minimum: 5, too_short: "hoo %{count}")
     t = Topic.new("title" => "uhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_maximum_with_message
     Topic.validates_length_of(:title, maximum: 5, message: "boo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["boo 5"], t.errors[:title]
   end
 
   def test_validates_length_of_custom_errors_for_in
     Topic.validates_length_of(:title, in: 10..20, message: "hoo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 10"], t.errors["title"]
 
     t = Topic.new("title" => "uhohuhohuhohuhohuhohuhohuhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 20"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_maximum_with_too_long
     Topic.validates_length_of(:title, maximum: 5, too_long: "hoo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -233,29 +233,29 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, minimum: 3, maximum: 5, too_short: "too short", too_long: "too long"
 
     t = Topic.new(title: "a")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["too short"], t.errors["title"]
 
     t = Topic.new(title: "aaaaaa")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["too long"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_is_with_message
     Topic.validates_length_of(:title, is: 5, message: "boo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["boo 5"], t.errors["title"]
   end
 
   def test_validates_length_of_custom_errors_for_is_with_wrong_length
     Topic.validates_length_of(:title, is: 5, wrong_length: "hoo %{count}")
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["hoo 5"], t.errors["title"]
   end
 
@@ -263,11 +263,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, minimum: 5
 
     t = Topic.new("title" => "一二三四五", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "一二三四"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too short (minimum is 5 characters)"], t.errors["title"]
   end
 
@@ -275,11 +275,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, maximum: 5
 
     t = Topic.new("title" => "一二三四五", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "一二34五六"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too long (maximum is 5 characters)"], t.errors["title"]
   end
 
@@ -287,12 +287,12 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, :content, within: 3..5)
 
     t = Topic.new("title" => "一二", "content" => "12三四五六七")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["is too short (minimum is 3 characters)"], t.errors[:title]
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:content]
     t.title = "一二三"
     t.content = "12三"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_optionally_validates_length_of_using_within_utf8
@@ -312,11 +312,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, is: 5
 
     t = Topic.new("title" => "一二345", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "一二345六"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is the wrong length (should be 5 characters)"], t.errors["title"]
   end
 
@@ -324,11 +324,11 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:approved, is: 4)
 
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever", approved: 1)
-    assert t.invalid?
-    assert t.errors[:approved].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:approved], :any?
 
     t = Topic.new("title" => "uhohuhoh", "content" => "whatever", approved: 1234)
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_for_ruby_class
@@ -336,12 +336,12 @@ class LengthValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Pix"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is too short (minimum is 5 characters)"], p.errors[:karma]
 
     p.karma = "The Smiths"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -350,80 +350,80 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of(:title, within: 5..Float::INFINITY)
 
     t = Topic.new("title" => "1234")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
 
     t.title = "12345"
-    assert t.valid?
+    assert_predicate t, :valid?
 
     Topic.validates_length_of(:author_name, maximum: Float::INFINITY)
 
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.author_name = "A very long author name that should still be valid." * 100
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_maximum_should_not_allow_nil_when_nil_not_allowed
     Topic.validates_length_of :title, maximum: 10, allow_nil: false
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_validates_length_of_using_maximum_should_not_allow_nil_and_empty_string_when_blank_not_allowed
     Topic.validates_length_of :title, maximum: 10, allow_blank: false
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_validates_length_of_using_both_minimum_and_maximum_should_not_allow_nil
     Topic.validates_length_of :title, minimum: 5, maximum: 10
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
   end
 
   def test_validates_length_of_using_minimum_0_should_not_allow_nil
     Topic.validates_length_of :title, minimum: 0
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_is_0_should_not_allow_nil
     Topic.validates_length_of :title, is: 0
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_with_diff_in_option
     Topic.validates_length_of(:title, is: 5)
     Topic.validates_length_of(:title, is: 5, if: Proc.new { false })
 
-    assert Topic.new("title" => "david").valid?
-    assert Topic.new("title" => "david2").invalid?
+    assert_predicate Topic.new("title" => "david"), :valid?
+    assert_predicate Topic.new("title" => "david2"), :invalid?
   end
 
   def test_validates_length_of_using_proc_as_maximum
     Topic.validates_length_of :title, maximum: ->(model) { 5 }
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "notvalid"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_length_of_using_proc_as_maximum_with_model_method
@@ -431,14 +431,14 @@ class LengthValidationTest < ActiveModel::TestCase
     Topic.validates_length_of :title, maximum: Proc.new(&:max_title_length)
 
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.valid?
+    assert_predicate t, :valid?
 
     t.title = "notvalid"
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["is too long (maximum is 5 characters)"], t.errors[:title]
 
     t.title = ""
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 end
diff --git a/activemodel/test/cases/validations/numericality_validation_test.rb b/activemodel/test/cases/validations/numericality_validation_test.rb
index 5413255e6b..01b78ae72e 100644
--- a/activemodel/test/cases/validations/numericality_validation_test.rb
+++ b/activemodel/test/cases/validations/numericality_validation_test.rb
@@ -237,13 +237,13 @@ class NumericalityValidationTest < ActiveModel::TestCase
     Topic.validates_numericality_of :approved, less_than: 4, message: "smaller than %{count}"
     topic = Topic.new("title" => "numeric test", "approved" => 10)
 
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["smaller than 4"], topic.errors[:approved]
 
     Topic.validates_numericality_of :approved, greater_than: 4, message: "greater than %{count}"
     topic = Topic.new("title" => "numeric test", "approved" => 1)
 
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["greater than 4"], topic.errors[:approved]
   end
 
@@ -252,12 +252,12 @@ class NumericalityValidationTest < ActiveModel::TestCase
 
     p = Person.new
     p.karma = "Pix"
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["is not a number"], p.errors[:karma]
 
     p.karma = "1234"
-    assert p.valid?
+    assert_predicate p, :valid?
   ensure
     Person.clear_validators!
   end
@@ -268,7 +268,7 @@ class NumericalityValidationTest < ActiveModel::TestCase
     topic = Topic.new
     topic.approved = (base + 1).to_s
 
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
   end
 
   def test_validates_numericality_with_invalid_args
diff --git a/activemodel/test/cases/validations/presence_validation_test.rb b/activemodel/test/cases/validations/presence_validation_test.rb
index 22c2f0af87..c3eca41070 100644
--- a/activemodel/test/cases/validations/presence_validation_test.rb
+++ b/activemodel/test/cases/validations/presence_validation_test.rb
@@ -17,25 +17,25 @@ class PresenceValidationTest < ActiveModel::TestCase
     Topic.validates_presence_of(:title, :content)
 
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:title]
     assert_equal ["can't be blank"], t.errors[:content]
 
     t.title = "something"
     t.content = "   "
 
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:content]
 
     t.content = "like stuff"
 
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_accepts_array_arguments
     Topic.validates_presence_of %w(title content)
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:title]
     assert_equal ["can't be blank"], t.errors[:content]
   end
@@ -43,7 +43,7 @@ class PresenceValidationTest < ActiveModel::TestCase
   def test_validates_acceptance_of_with_custom_error_using_quotes
     Person.validates_presence_of :karma, message: "This string contains 'single' and \"double\" quotes"
     p = Person.new
-    assert p.invalid?
+    assert_predicate p, :invalid?
     assert_equal "This string contains 'single' and \"double\" quotes", p.errors[:karma].last
   end
 
@@ -51,24 +51,24 @@ class PresenceValidationTest < ActiveModel::TestCase
     Person.validates_presence_of :karma
 
     p = Person.new
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["can't be blank"], p.errors[:karma]
 
     p.karma = "Cold"
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 
   def test_validates_presence_of_for_ruby_class_with_custom_reader
     CustomReader.validates_presence_of :karma
 
     p = CustomReader.new
-    assert p.invalid?
+    assert_predicate p, :invalid?
 
     assert_equal ["can't be blank"], p.errors[:karma]
 
     p[:karma] = "Cold"
-    assert p.valid?
+    assert_predicate p, :valid?
   end
 
   def test_validates_presence_of_with_allow_nil_option
@@ -78,7 +78,7 @@ class PresenceValidationTest < ActiveModel::TestCase
     assert t.valid?, t.errors.full_messages
 
     t.title = ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["can't be blank"], t.errors[:title]
 
     t.title = "  "
diff --git a/activemodel/test/cases/validations/validates_test.rb b/activemodel/test/cases/validations/validates_test.rb
index 7f32f5dc74..80c347703a 100644
--- a/activemodel/test/cases/validations/validates_test.rb
+++ b/activemodel/test/cases/validations/validates_test.rb
@@ -37,7 +37,7 @@ class ValidatesTest < ActiveModel::TestCase
 
     person = Person.new
     person.title = 123
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_built_in_validation_and_options
@@ -71,7 +71,7 @@ class ValidatesTest < ActiveModel::TestCase
   def test_validates_with_if_as_shared_conditions
     Person.validates :karma, presence: true, email: true, if: :condition_is_false
     person = Person.new
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_unless_as_local_conditions
@@ -84,40 +84,40 @@ class ValidatesTest < ActiveModel::TestCase
   def test_validates_with_unless_shared_conditions
     Person.validates :karma, presence: true, email: true, unless: :condition_is_true
     person = Person.new
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_allow_nil_shared_conditions
     Person.validates :karma, length: { minimum: 20 }, email: true, allow_nil: true
     person = Person.new
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_regexp
     Person.validates :karma, format: /positive|negative/
     person = Person.new
-    assert person.invalid?
+    assert_predicate person, :invalid?
     assert_equal ["is invalid"], person.errors[:karma]
     person.karma = "positive"
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_array
     Person.validates :gender, inclusion: %w(m f)
     person = Person.new
-    assert person.invalid?
+    assert_predicate person, :invalid?
     assert_equal ["is not included in the list"], person.errors[:gender]
     person.gender = "m"
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_range
     Person.validates :karma, length: 6..20
     person = Person.new
-    assert person.invalid?
+    assert_predicate person, :invalid?
     assert_equal ["is too short (minimum is 6 characters)"], person.errors[:karma]
     person.karma = "something"
-    assert person.valid?
+    assert_predicate person, :valid?
   end
 
   def test_validates_with_validator_class_and_options
@@ -159,7 +159,7 @@ class ValidatesTest < ActiveModel::TestCase
     topic = Topic.new
     topic.title = "What's happening"
     topic.title_confirmation = "Not this"
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["Y U NO CONFIRM"], topic.errors[:title_confirmation]
   end
 end
diff --git a/activemodel/test/cases/validations/with_validation_test.rb b/activemodel/test/cases/validations/with_validation_test.rb
index 13ef5e6a31..8239792c79 100644
--- a/activemodel/test/cases/validations/with_validation_test.rb
+++ b/activemodel/test/cases/validations/with_validation_test.rb
@@ -65,7 +65,7 @@ class ValidatesWithTest < ActiveModel::TestCase
   test "with multiple classes" do
     Topic.validates_with(ValidatorThatAddsErrors, OtherValidatorThatAddsErrors)
     topic = Topic.new
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_includes topic.errors[:base], ERROR_MESSAGE
     assert_includes topic.errors[:base], OTHER_ERROR_MESSAGE
   end
@@ -79,21 +79,21 @@ class ValidatesWithTest < ActiveModel::TestCase
     validator.expect(:is_a?, false, [String])
 
     Topic.validates_with(validator, if: :condition_is_true, foo: :bar)
-    assert topic.valid?
+    assert_predicate topic, :valid?
     validator.verify
   end
 
   test "validates_with with options" do
     Topic.validates_with(ValidatorThatValidatesOptions, field: :first_name)
     topic = Topic.new
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_includes topic.errors[:base], ERROR_MESSAGE
   end
 
   test "validates_with each validator" do
     Topic.validates_with(ValidatorPerEachAttribute, attributes: [:title, :content])
     topic = Topic.new title: "Title", content: "Content"
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_equal ["Value is Title"], topic.errors[:title]
     assert_equal ["Value is Content"], topic.errors[:content]
   end
@@ -113,28 +113,28 @@ class ValidatesWithTest < ActiveModel::TestCase
   test "each validator skip nil values if :allow_nil is set to true" do
     Topic.validates_with(ValidatorPerEachAttribute, attributes: [:title, :content], allow_nil: true)
     topic = Topic.new content: ""
-    assert topic.invalid?
-    assert topic.errors[:title].empty?
+    assert_predicate topic, :invalid?
+    assert_empty topic.errors[:title]
     assert_equal ["Value is "], topic.errors[:content]
   end
 
   test "each validator skip blank values if :allow_blank is set to true" do
     Topic.validates_with(ValidatorPerEachAttribute, attributes: [:title, :content], allow_blank: true)
     topic = Topic.new content: ""
-    assert topic.valid?
-    assert topic.errors[:title].empty?
-    assert topic.errors[:content].empty?
+    assert_predicate topic, :valid?
+    assert_empty topic.errors[:title]
+    assert_empty topic.errors[:content]
   end
 
   test "validates_with can validate with an instance method" do
     Topic.validates :title, with: :my_validation
 
     topic = Topic.new title: "foo"
-    assert topic.valid?
-    assert topic.errors[:title].empty?
+    assert_predicate topic, :valid?
+    assert_empty topic.errors[:title]
 
     topic = Topic.new
-    assert !topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["is missing"], topic.errors[:title]
   end
 
@@ -142,8 +142,8 @@ class ValidatesWithTest < ActiveModel::TestCase
     Topic.validates :title, :content, with: :my_validation_with_arg
 
     topic = Topic.new title: "foo"
-    assert !topic.valid?
-    assert topic.errors[:title].empty?
+    assert_not_predicate topic, :valid?
+    assert_empty topic.errors[:title]
     assert_equal ["is missing"], topic.errors[:content]
   end
 end
diff --git a/activemodel/test/cases/validations_test.rb b/activemodel/test/cases/validations_test.rb
index ab8c41bbd0..7776233db5 100644
--- a/activemodel/test/cases/validations_test.rb
+++ b/activemodel/test/cases/validations_test.rb
@@ -30,7 +30,7 @@ class ValidationsTest < ActiveModel::TestCase
   def test_single_attr_validation_and_error_msg
     r = Reply.new
     r.title = "There's no content!"
-    assert r.invalid?
+    assert_predicate r, :invalid?
     assert r.errors[:content].any?, "A reply without content should mark that attribute as invalid"
     assert_equal ["is Empty"], r.errors["content"], "A reply without content should contain an error"
     assert_equal 1, r.errors.count
@@ -38,7 +38,7 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_double_attr_validation_and_error_msg
     r = Reply.new
-    assert r.invalid?
+    assert_predicate r, :invalid?
 
     assert r.errors[:title].any?, "A reply without title should mark that attribute as invalid"
     assert_equal ["is Empty"], r.errors["title"], "A reply without title should contain an error"
@@ -111,8 +111,8 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_errors_empty_after_errors_on_check
     t = Topic.new
-    assert t.errors[:id].empty?
-    assert t.errors.empty?
+    assert_empty t.errors[:id]
+    assert_empty t.errors
   end
 
   def test_validates_each
@@ -122,7 +122,7 @@ class ValidationsTest < ActiveModel::TestCase
       hits += 1
     end
     t = Topic.new("title" => "valid", "content" => "whatever")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal 4, hits
     assert_equal %w(gotcha gotcha), t.errors[:title]
     assert_equal %w(gotcha gotcha), t.errors[:content]
@@ -135,7 +135,7 @@ class ValidationsTest < ActiveModel::TestCase
       hits += 1
     end
     t = CustomReader.new("title" => "valid", "content" => "whatever")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal 4, hits
     assert_equal %w(gotcha gotcha), t.errors[:title]
     assert_equal %w(gotcha gotcha), t.errors[:content]
@@ -146,16 +146,16 @@ class ValidationsTest < ActiveModel::TestCase
   def test_validate_block
     Topic.validate { errors.add("title", "will never be valid") }
     t = Topic.new("title" => "Title", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["will never be valid"], t.errors["title"]
   end
 
   def test_validate_block_with_params
     Topic.validate { |topic| topic.errors.add("title", "will never be valid") }
     t = Topic.new("title" => "Title", "content" => "whatever")
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
     assert_equal ["will never be valid"], t.errors["title"]
   end
 
@@ -214,7 +214,7 @@ class ValidationsTest < ActiveModel::TestCase
   def test_errors_conversions
     Topic.validates_presence_of %w(title content)
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     xml = t.errors.to_xml
     assert_match %r{<errors>}, xml
@@ -232,14 +232,14 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates_length_of :title, minimum: 2
 
     t = Topic.new("title" => "")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal "can't be blank", t.errors["title"].first
     Topic.validates_presence_of :title, :author_name
     Topic.validate { errors.add("author_email_address", "will never be valid") }
     Topic.validates_length_of :title, :content, minimum: 2
 
     t = Topic.new title: ""
-    assert t.invalid?
+    assert_predicate t, :invalid?
 
     assert_equal :title, key = t.errors.keys[0]
     assert_equal "can't be blank", t.errors[key][0]
@@ -258,8 +258,8 @@ class ValidationsTest < ActiveModel::TestCase
     t = Topic.new(title: "")
 
     # If block should not fire
-    assert t.valid?
-    assert t.author_name.nil?
+    assert_predicate t, :valid?
+    assert_predicate t.author_name, :nil?
 
     # If block should fire
     assert t.invalid?(:update)
@@ -270,18 +270,18 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates_presence_of :title
 
     t = Topic.new
-    assert t.invalid?
-    assert t.errors[:title].any?
+    assert_predicate t, :invalid?
+    assert_predicate t.errors[:title], :any?
 
     t.title = "Things are going to change"
-    assert !t.invalid?
+    assert_not_predicate t, :invalid?
   end
 
   def test_validation_with_message_as_proc
     Topic.validates_presence_of(:title, message: proc { "no blanks here".upcase })
 
     t = Topic.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["NO BLANKS HERE"], t.errors[:title]
   end
 
@@ -331,13 +331,13 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates :content, length: { minimum: 10 }
 
     topic = Topic.new
-    assert topic.invalid?
+    assert_predicate topic, :invalid?
     assert_equal 3, topic.errors.size
 
     topic.title = "Some Title"
     topic.author_name = "Some Author"
     topic.content = "Some Content Whose Length is more than 10."
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_validate
@@ -381,7 +381,7 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_strict_validation_not_fails
     Topic.validates :title, strict: true, presence: true
-    assert Topic.new(title: "hello").valid?
+    assert_predicate Topic.new(title: "hello"), :valid?
   end
 
   def test_strict_validation_particular_validator
@@ -414,7 +414,7 @@ class ValidationsTest < ActiveModel::TestCase
 
   def test_validates_with_false_hash_value
     Topic.validates :title, presence: false
-    assert Topic.new.valid?
+    assert_predicate Topic.new, :valid?
   end
 
   def test_strict_validation_error_message
@@ -439,19 +439,19 @@ class ValidationsTest < ActiveModel::TestCase
 
     duped = topic.dup
     duped.title = nil
-    assert duped.invalid?
+    assert_predicate duped, :invalid?
 
     topic.title = nil
     duped.title = "Mathematics"
-    assert topic.invalid?
-    assert duped.valid?
+    assert_predicate topic, :invalid?
+    assert_predicate duped, :valid?
   end
 
   def test_validation_with_message_as_proc_that_takes_a_record_as_a_parameter
     Topic.validates_presence_of(:title, message: proc { |record| "You have failed me for the last time, #{record.author_name}." })
 
     t = Topic.new(author_name: "Admiral")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["You have failed me for the last time, Admiral."], t.errors[:title]
   end
 
@@ -459,7 +459,7 @@ class ValidationsTest < ActiveModel::TestCase
     Topic.validates_presence_of(:title, message: proc { |record, data| "#{data[:attribute]} is missing. You have failed me for the last time, #{record.author_name}." })
 
     t = Topic.new(author_name: "Admiral")
-    assert t.invalid?
+    assert_predicate t, :invalid?
     assert_equal ["Title is missing. You have failed me for the last time, Admiral."], t.errors[:title]
   end
 end
diff --git a/activerecord/.gitignore b/activerecord/.gitignore
new file mode 100644
index 0000000000..884ee009eb
--- /dev/null
+++ b/activerecord/.gitignore
@@ -0,0 +1,3 @@
+/sqlnet.log
+/test/config.yml
+/test/fixtures/*.sqlite*
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index efe555374a..325c4abfc8 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,634 +1,21 @@
-*   Fix relation merger issue with `left_outer_joins`.
+## Rails 6.0.0.alpha (Unreleased) ##
 
-    *Mehmet Emin İNAÇ*
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-*   Don't allow destroyed object mutation after `save` or `save!` is called.
+    *Jeremy Daer*
 
-    *Ryuta Kamizono*
+*   Deprecate `update_attributes`/`!` in favor of `update`/`!`.
 
-*   Take into account association conditions when deleting through records.
+    *Eddie Lebow*
 
-    Fixes #18424.
-
-    *Piotr Jakubowski*
-
-*   Fix nested `has_many :through` associations on unpersisted parent instances.
-
-    For example, if you have
-
-        class Post < ActiveRecord::Base
-          belongs_to :author
-          has_many :books, through: :author
-          has_many :subscriptions, through: :books
-        end
-
-        class Author < ActiveRecord::Base
-          has_one :post
-          has_many :books
-          has_many :subscriptions, through: :books
-        end
-
-        class Book < ActiveRecord::Base
-          belongs_to :author
-          has_many :subscriptions
-        end
-
-        class Subscription < ActiveRecord::Base
-          belongs_to :book
-        end
-
-    Before:
-
-    If `post` is not persisted, then `post.subscriptions` will be empty.
-
-    After:
-
-    If `post` is not persisted, then `post.subscriptions` can be set and used
-    just like it would if `post` were persisted.
-
-    Fixes #16313.
-
-    *Zoltan Kiss*
-
-*   Fixed inconsistency with `first(n)` when used with `limit()`.
-    The `first(n)` finder now respects the `limit()`, making it consistent
-    with `relation.to_a.first(n)`, and also with the behavior of `last(n)`.
-
-    Fixes #23979.
-
-    *Brian Christian*
-
-*   Use `count(:all)` in `HasManyAssociation#count_records` to prevent invalid
-    SQL queries for association counting.
-
-    *Klas Eskilson*
-
-*   Fix to invoke callbacks when using `update_attribute`.
-
-    *Mike Busch*
-
-*   Fix `count(:all)` to correctly work `distinct` with custom SELECT list.
-
-    *Ryuta Kamizono*
-
-*   Using subselect for `delete_all` with `limit` or `offset`.
-
-    *Ryuta Kamizono*
-
-*   Undefine attribute methods on descendants when resetting column
-    information.
-
-    *Chris Salzberg*
-
-*   Log database query callers
-
-    Add `verbose_query_logs` configuration option to display the caller
-    of database queries in the log to facilitate N+1 query resolution
-    and other debugging.
-
-    Enabled in development only for new and upgraded applications. Not
-    recommended for use in the production environment since it relies
-    on Ruby's `Kernel#caller_locations` which is fairly slow.
-
-    *Olivier Lacan*
-
-*   Fix conflicts `counter_cache` with `touch: true` by optimistic locking.
-
-    ```
-    # create_table :posts do |t|
-    #   t.integer :comments_count, default: 0
-    #   t.integer :lock_version
-    #   t.timestamps
-    # end
-    class Post < ApplicationRecord
-    end
-
-    # create_table :comments do |t|
-    #   t.belongs_to :post
-    # end
-    class Comment < ApplicationRecord
-      belongs_to :post, touch: true, counter_cache: true
-    end
-    ```
-
-    Before:
-    ```
-    post = Post.create!
-    # => begin transaction
-         INSERT INTO "posts" ("created_at", "updated_at", "lock_version")
-         VALUES ("2017-12-11 21:27:11.387397", "2017-12-11 21:27:11.387397", 0)
-         commit transaction
-
-    comment = Comment.create!(post: post)
-    # => begin transaction
-         INSERT INTO "comments" ("post_id") VALUES (1)
-
-         UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) + 1,
-         "lock_version" = COALESCE("lock_version", 0) + 1 WHERE "posts"."id" = 1
-
-         UPDATE "posts" SET "updated_at" = '2017-12-11 21:27:11.398330',
-         "lock_version" = 1 WHERE "posts"."id" = 1 AND "posts"."lock_version" = 0
-         rollback transaction
-    # => ActiveRecord::StaleObjectError: Attempted to touch a stale object: Post.
-
-    Comment.take.destroy!
-    # => begin transaction
-         DELETE FROM "comments" WHERE "comments"."id" = 1
-
-         UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) - 1,
-         "lock_version" = COALESCE("lock_version", 0) + 1 WHERE "posts"."id" = 1
-
-         UPDATE "posts" SET "updated_at" = '2017-12-11 21:42:47.785901',
-         "lock_version" = 1 WHERE "posts"."id" = 1 AND "posts"."lock_version" = 0
-         rollback transaction
-    # => ActiveRecord::StaleObjectError: Attempted to touch a stale object: Post.
-    ```
-
-    After:
-    ```
-    post = Post.create!
-    # => begin transaction
-         INSERT INTO "posts" ("created_at", "updated_at", "lock_version")
-         VALUES ("2017-12-11 21:27:11.387397", "2017-12-11 21:27:11.387397", 0)
-         commit transaction
-
-    comment = Comment.create!(post: post)
-    # => begin transaction
-         INSERT INTO "comments" ("post_id") VALUES (1)
-
-         UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) + 1,
-         "lock_version" = COALESCE("lock_version", 0) + 1,
-         "updated_at" = '2017-12-11 21:37:09.802642' WHERE "posts"."id" = 1
-         commit transaction
-
-    comment.destroy!
-    # => begin transaction
-         DELETE FROM "comments" WHERE "comments"."id" = 1
-
-         UPDATE "posts" SET "comments_count" = COALESCE("comments_count", 0) - 1,
-         "lock_version" = COALESCE("lock_version", 0) + 1,
-         "updated_at" = '2017-12-11 21:39:02.685520' WHERE "posts"."id" = 1
-         commit transaction
-    ```
-
-    Fixes #31199.
-
-    *bogdanvlviv*
-
-*   Add support for PostgreSQL operator classes to `add_index`.
-
-    Example:
-
-        add_index :users, :name, using: :gist, opclass: { name: :gist_trgm_ops }
-
-    *Greg Navis*
-
-*   Don't allow scopes to be defined which conflict with instance methods on `Relation`.
-
-    Fixes #31120.
-
-    *kinnrot*
-
-
-## Rails 5.2.0.beta2 (November 28, 2017) ##
-
-*   No changes.
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Add new error class `QueryCanceled` which will be raised
-    when canceling statement due to user request.
-
-    *Ryuta Kamizono*
-
-*   Add `#up_only` to database migrations for code that is only relevant when
-    migrating up, e.g. populating a new column.
-
-    *Rich Daley*
-
-*   Require raw SQL fragments to be explicitly marked when used in
-    relation query methods.
-
-    Before:
-    ```
-    Article.order("LENGTH(title)")
-    ```
-
-    After:
-    ```
-    Article.order(Arel.sql("LENGTH(title)"))
-    ```
-
-    This prevents SQL injection if applications use the [strongly
-    discouraged] form `Article.order(params[:my_order])`, under the
-    mistaken belief that only column names will be accepted.
-
-    Raw SQL strings will now cause a deprecation warning, which will
-    become an UnknownAttributeReference error in Rails 6.0. Applications
-    can opt in to the future behavior by setting `allow_unsafe_raw_sql`
-    to `:disabled`.
-
-    Common and judged-safe string values (such as simple column
-    references) are unaffected:
-    ```
-    Article.order("title DESC")
-    ```
-
-    *Ben Toews*
-
-*   `update_all` will now pass its values to `Type#cast` before passing them to
-    `Type#serialize`. This means that `update_all(foo: 'true')` will properly
-    persist a boolean.
-
-    *Sean Griffin*
-
-*   Add new error class `StatementTimeout` which will be raised
-    when statement timeout exceeded.
-
-    *Ryuta Kamizono*
-
-*   Fix `bin/rails db:migrate` with specified `VERSION`.
-    `bin/rails db:migrate` with empty VERSION behaves as without `VERSION`.
-    Check a format of `VERSION`: Allow a migration version number
-    or name of a migration file. Raise error if format of `VERSION` is invalid.
-    Raise error if target migration doesn't exist.
-
-    *bogdanvlviv*
-
-*   Fixed a bug where column orders for an index weren't written to
-    `db/schema.rb` when using the sqlite adapter.
-
-    Fixes #30902.
-
-    *Paul Kuruvilla*
-
-*   Remove deprecated method `#sanitize_conditions`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated method `#scope_chain`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated configuration `.error_on_ignored_order_or_limit`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated arguments from `#verify!`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated argument `name` from `#indexes`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated method `ActiveRecord::Migrator.schema_migrations_table_name`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated method `supports_primary_key?`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated method `supports_migrations?`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated methods `initialize_schema_migrations_table` and `initialize_internal_metadata_table`.
-
-    *Rafael Mendonça França*
-
-*   Raises when calling `lock!` in a dirty record.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated support to passing a class to `:class_name` on associations.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated argument `default` from `index_name_exists?`.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated support to `quoted_id` when typecasting an Active Record object.
-
-    *Rafael Mendonça França*
-
-*   Fix `bin/rails db:setup` and `bin/rails db:test:prepare` create  wrong
-    ar_internal_metadata's data for a test database.
-
-    Before:
-    ```
-    $ RAILS_ENV=test rails dbconsole
-    > SELECT * FROM ar_internal_metadata;
-    key|value|created_at|updated_at
-    environment|development|2017-09-11 23:14:10.815679|2017-09-11 23:14:10.815679
-    ```
-
-    After:
-    ```
-    $ RAILS_ENV=test rails dbconsole
-    > SELECT * FROM ar_internal_metadata;
-    key|value|created_at|updated_at
-    environment|test|2017-09-11 23:14:10.815679|2017-09-11 23:14:10.815679
-    ```
-
-    Fixes #26731.
-
-    *bogdanvlviv*
-
-*   Fix longer sequence name detection for serial columns.
-
-    Fixes #28332.
-
-    *Ryuta Kamizono*
-
-*   MySQL: Don't lose `auto_increment: true` in the `db/schema.rb`.
-
-    Fixes #30894.
-
-    *Ryuta Kamizono*
-
-*   Fix `COUNT(DISTINCT ...)` for `GROUP BY` with `ORDER BY` and `LIMIT`.
-
-    Fixes #30886.
-
-    *Ryuta Kamizono*
-
-*   PostgreSQL `tsrange` now preserves subsecond precision.
-
-    PostgreSQL 9.1+ introduced range types, and Rails added support for using
-    this datatype in Active Record. However, the serialization of
-    `PostgreSQL::OID::Range` was incomplete, because it did not properly
-    cast the bounds that make up the range. This led to subseconds being
-    dropped in SQL commands:
-
-    Before:
-
-        connection.type_cast(tsrange.serialize(range_value))
-        # => "[2010-01-01 13:30:00 UTC,2011-02-02 19:30:00 UTC)"
-
-    Now:
-
-        connection.type_cast(tsrange.serialize(range_value))
-        # => "[2010-01-01 13:30:00.670277,2011-02-02 19:30:00.745125)"
-
-    *Thomas Cannon*
-
-*   Passing a `Set` to `Relation#where` now behaves the same as passing an
-    array.
-
-    *Sean Griffin*
-
-*   Use given algorithm while removing index from database.
-
-    Fixes #24190.
-
-    *Mehmet Emin İNAÇ*
-
-*   Update payload names for `sql.active_record` instrumentation to be
-    more descriptive.
-
-    Fixes #30586.
-
-    *Jeremy Green*
-
-*   Add new error class `LockWaitTimeout` which will be raised
-    when lock wait timeout exceeded.
-
-    *Gabriel Courtemanche*
-
-*   Remove deprecated `#migration_keys`.
-
-    *Ryuta Kamizono*
-
-*   Automatically guess the inverse associations for STI.
-
-    *Yuichiro Kaneko*
-
-*   Ensure `sum` honors `distinct` on `has_many :through` associations
-
-    Fixes #16791.
-
-    *Aaron Wortham*
-
-*   Add `binary` fixture helper method.
-
-    *Atsushi Yoshida*
-
-*   When using `Relation#or`, extract the common conditions and put them before the OR condition.
-
-    *Maxime Handfield Lapointe*
-
-*   `Relation#or` now accepts two relations who have different values for
-    `references` only, as `references` can be implicitly called by `where`.
-
-    Fixes #29411.
-
-    *Sean Griffin*
-
-*   `ApplicationRecord` is no longer generated when generating models. If you
-    need to generate it, it can be created with `rails g application_record`.
-
-    *Lisa Ugray*
-
-*   Fix `COUNT(DISTINCT ...)` with `ORDER BY` and `LIMIT` to keep the existing select list.
-
-    *Ryuta Kamizono*
-
-*   When a `has_one` association is destroyed by `dependent: destroy`,
-    `destroyed_by_association` will now be set to the reflection, matching the
-    behaviour of `has_many` associations.
-
-    *Lisa Ugray*
-
-*   Fix `unscoped(where: [columns])` removing the wrong bind values
-
-    When the `where` is called on a relation after a `or`, unscoping the column of that later `where` removed
-    bind values used by the `or` instead. (possibly other cases too)
-
-    ```
-    Post.where(id: 1).or(Post.where(id: 2)).where(foo: 3).unscope(where: :foo).to_sql
-    # Currently:
-    #     SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 2 OR "posts"."id" = 3)
-    # With fix:
-    #     SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 1 OR "posts"."id" = 2)
-    ```
-
-    *Maxime Handfield Lapointe*
-
-*   Values constructed using multi-parameter assignment will now use the
-    post-type-cast value for rendering in single-field form inputs.
-
-    *Sean Griffin*
-
-*   `Relation#joins` is no longer affected by the target model's
-    `current_scope`, with the exception of `unscoped`.
-
-    Fixes #29338.
-
-    *Sean Griffin*
-
-*   Change sqlite3 boolean serialization to use 1 and 0
-
-    SQLite natively recognizes 1 and 0 as true and false, but does not natively
-    recognize 't' and 'f' as was previously serialized.
-
-    This change in serialization requires a migration of stored boolean data
-    for SQLite databases, so it's implemented behind a configuration flag
-    whose default false value is deprecated.
-
-    *Lisa Ugray*
-
-*   Skip query caching when working with batches of records (`find_each`, `find_in_batches`,
-    `in_batches`).
-
-    Previously, records would be fetched in batches, but all records would be retained in memory
-    until the end of the request or job.
-
-    *Eugene Kenny*
-
-*   Prevent errors raised by `sql.active_record` notification subscribers from being converted into
-    `ActiveRecord::StatementInvalid` exceptions.
-
-    *Dennis Taylor*
-
-*   Fix eager loading/preloading association with scope including joins.
-
-    Fixes #28324.
-
-    *Ryuta Kamizono*
-
-*   Fix transactions to apply state to child transactions
-
-    Previously, if you had a nested transaction and the outer transaction was rolledback, the record from the
-    inner transaction would still be marked as persisted.
-
-    This change fixes that by applying the state of the parent transaction to the child transaction when the
-    parent transaction is rolledback. This will correctly mark records from the inner transaction as not persisted.
-
-    *Eileen M. Uchitelle*, *Aaron Patterson*
-
-*   Deprecate `set_state` method in `TransactionState`
-
-    Deprecated the `set_state` method in favor of setting the state via specific methods. If you need to mark the
-    state of the transaction you can now use `rollback!`, `commit!` or `nullify!` instead of
-    `set_state(:rolledback)`, `set_state(:committed)`, or `set_state(nil)`.
-
-    *Eileen M. Uchitelle*, *Aaron Patterson*
-
-*   Deprecate delegating to `arel` in `Relation`.
-
-    *Ryuta Kamizono*
-
-*   Fix eager loading to respect `store_full_sti_class` setting.
-
-    *Ryuta Kamizono*
-
-*   Query cache was unavailable when entering the `ActiveRecord::Base.cache` block
-    without being connected.
-
-    *Tsukasa Oishi*
-
-*   Previously, when building records using a `has_many :through` association,
-    if the child records were deleted before the parent was saved, they would
-    still be persisted. Now, if child records are deleted before the parent is saved
-    on a `has_many :through` association, the child records will not be persisted.
-
-    *Tobias Kraze*
-
-*   Merging two relations representing nested joins no longer transforms the joins of
-    the merged relation into LEFT OUTER JOIN. Example to clarify:
-
-    ```
-    Author.joins(:posts).merge(Post.joins(:comments))
-    # Before the change:
-    #=> SELECT ... FROM authors INNER JOIN posts ON ... LEFT OUTER JOIN comments ON...
-
-    # After the change:
-    #=> SELECT ... FROM authors INNER JOIN posts ON ... INNER JOIN comments ON...
-    ```
-
-    TODO: Add to the Rails 5.2 upgrade guide
-
-    *Maxime Handfield Lapointe*
-
-*   `ActiveRecord::Persistence#touch` does not work well when optimistic locking enabled and
-    `locking_column`, without default value, is null in the database.
-
-    *bogdanvlviv*
-
-*   Fix destroying existing object does not work well when optimistic locking enabled and
-    `locking_column` is null in the database.
-
-    *bogdanvlviv*
-
-*   Use bulk INSERT to insert fixtures for better performance.
-
-    *Kir Shatrov*
-
-*   Prevent creation of bind param if casted value is nil.
-
-    *Ryuta Kamizono*
-
-*   Deprecate passing arguments and block at the same time to `count` and `sum` in `ActiveRecord::Calculations`.
-
-    *Ryuta Kamizono*
-
-*   Loading model schema from database is now thread-safe.
-
-    Fixes #28589.
-
-    *Vikrant Chaudhary*, *David Abdemoulaie*
-
-*   Add `ActiveRecord::Base#cache_version` to support recyclable cache keys via the new versioned entries
-    in `ActiveSupport::Cache`. This also means that `ActiveRecord::Base#cache_key` will now return a stable key
-    that does not include a timestamp any more.
-
-    NOTE: This feature is turned off by default, and `#cache_key` will still return cache keys with timestamps
-    until you set `ActiveRecord::Base.cache_versioning = true`. That's the setting for all new apps on Rails 5.2+
+*   Add ActiveRecord::Base.create_or_find_by/! to deal with the SELECT/INSERT race condition in
+    ActiveRecord::Base.find_or_create_by/! by leaning on unique constraints in the database.
 
     *DHH*
 
-*   Respect `SchemaDumper.ignore_tables` in rake tasks for databases structure dump
-
-    *Rusty Geldmacher*, *Guillermo Iguaran*
-
-*   Add type caster to `RuntimeReflection#alias_name`
-
-    Fixes #28959.
+*   Add `Relation#pick` as short-hand for single-value plucks.
 
-    *Jon Moss*
-
-*   Deprecate `supports_statement_cache?`.
-
-    *Ryuta Kamizono*
-
-*   Raise error `UnknownMigrationVersionError` on the movement of migrations
-    when the current migration does not exist.
-
-    *bogdanvlviv*
-
-*   Fix `bin/rails db:forward` first migration.
-
-    *bogdanvlviv*
-
-*   Support Descending Indexes for MySQL.
-
-    MySQL 8.0.1 and higher supports descending indexes: `DESC` in an index definition is no longer ignored.
-    See https://dev.mysql.com/doc/refman/8.0/en/descending-indexes.html.
-
-    *Ryuta Kamizono*
-
-*   Fix inconsistency with changed attributes when overriding AR attribute reader.
-
-    *bogdanvlviv*
-
-*   When calling the dynamic fixture accessor method with no arguments, it now returns all fixtures of this type.
-    Previously this method always returned an empty array.
-
-    *Kevin McPhillips*
+    *DHH*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activerecord/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activerecord/CHANGELOG.md) for previous changes.
diff --git a/activerecord/activerecord.gemspec b/activerecord/activerecord.gemspec
index 8e42a11df4..b43e7c50f5 100644
--- a/activerecord/activerecord.gemspec
+++ b/activerecord/activerecord.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Object-relational mapper framework (part of Rails)."
   s.description = "Databases on Rails. Build a persistent domain model by mapping database tables to Ruby classes. Strong conventions for associations, validations, aggregations, migrations, and testing come baked-in."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activerecord/bin/test b/activerecord/bin/test
index 83c192531e..9ecf27ce67 100755
--- a/activerecord/bin/test
+++ b/activerecord/bin/test
@@ -1,6 +1,12 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
+adapter_index = ARGV.index("--adapter") || ARGV.index("-a")
+if adapter_index
+  ARGV.delete_at(adapter_index)
+  ENV["ARCONN"] = ARGV.delete_at(adapter_index).strip
+end
+
 COMPONENT_ROOT = File.expand_path("..", __dir__)
 require_relative "../../tools/test"
 
@@ -17,4 +23,5 @@ module Minitest
   end
 end
 
+Minitest.load_plugins
 Minitest.extensions.unshift "active_record"
diff --git a/activerecord/examples/.gitignore b/activerecord/examples/.gitignore
deleted file mode 100644
index 0dfc1cb7fb..0000000000
--- a/activerecord/examples/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-performance.sql
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index b4377ad6be..d43378c64f 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -163,6 +163,7 @@ module ActiveRecord
       "active_record/tasks/postgresql_database_tasks"
   end
 
+  autoload :TestDatabases, "active_record/test_databases"
   autoload :TestFixtures, "active_record/fixtures"
 
   def self.eager_load!
diff --git a/activerecord/lib/active_record/aggregations.rb b/activerecord/lib/active_record/aggregations.rb
index e5e89734d2..27a641f05b 100644
--- a/activerecord/lib/active_record/aggregations.rb
+++ b/activerecord/lib/active_record/aggregations.rb
@@ -35,7 +35,7 @@ module ActiveRecord
       # the database).
       #
       #   class Customer < ActiveRecord::Base
-      #     composed_of :balance, class_name: "Money", mapping: %w(amount currency)
+      #     composed_of :balance, class_name: "Money", mapping: %w(balance amount)
       #     composed_of :address, mapping: [ %w(address_street street), %w(address_city city) ]
       #   end
       #
@@ -177,9 +177,9 @@ module ActiveRecord
       #
       # Once a #composed_of relationship is specified for a model, records can be loaded from the database
       # by specifying an instance of the value object in the conditions hash. The following example
-      # finds all customers with +balance_amount+ equal to 20 and +balance_currency+ equal to "USD":
+      # finds all customers with +address_street+ equal to "May Street" and +address_city+ equal to "Chicago":
       #
-      #   Customer.where(balance: Money.new(20, "USD"))
+      #   Customer.where(address: Address.new("May Street", "Chicago"))
       #
       module ClassMethods
         # Adds reader and writer methods for manipulating a value object:
@@ -212,8 +212,7 @@ module ActiveRecord
         #
         # Option examples:
         #   composed_of :temperature, mapping: %w(reading celsius)
-        #   composed_of :balance, class_name: "Money", mapping: %w(balance amount),
-        #                         converter: Proc.new { |balance| balance.to_money }
+        #   composed_of :balance, class_name: "Money", mapping: %w(balance amount)
         #   composed_of :address, mapping: [ %w(address_street street), %w(address_city city) ]
         #   composed_of :gps_location
         #   composed_of :gps_location, allow_nil: true
diff --git a/activerecord/lib/active_record/association_relation.rb b/activerecord/lib/active_record/association_relation.rb
index 2b0b2864bc..403667fb70 100644
--- a/activerecord/lib/active_record/association_relation.rb
+++ b/activerecord/lib/active_record/association_relation.rb
@@ -2,8 +2,8 @@
 
 module ActiveRecord
   class AssociationRelation < Relation
-    def initialize(klass, table, predicate_builder, association)
-      super(klass, table, predicate_builder)
+    def initialize(klass, association)
+      super(klass)
       @association = association
     end
 
diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index ca1f9f1650..364f1fe74f 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -124,7 +124,7 @@ module ActiveRecord
       # Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the
       # through association's scope)
       def target_scope
-        AssociationRelation.create(klass, klass.arel_table, klass.predicate_builder, self).merge!(klass.all)
+        AssociationRelation.create(klass, self).merge!(klass.all)
       end
 
       def extensions
@@ -156,9 +156,9 @@ module ActiveRecord
         reset
       end
 
-      # We can't dump @reflection since it contains the scope proc
+      # We can't dump @reflection and @through_reflection since it contains the scope proc
       def marshal_dump
-        ivars = (instance_variables - [:@reflection]).map { |name| [name, instance_variable_get(name)] }
+        ivars = (instance_variables - [:@reflection, :@through_reflection]).map { |name| [name, instance_variable_get(name)] }
         [@reflection.name, ivars]
       end
 
diff --git a/activerecord/lib/active_record/associations/association_scope.rb b/activerecord/lib/active_record/associations/association_scope.rb
index 11967e0571..ad41ec8d2f 100644
--- a/activerecord/lib/active_record/associations/association_scope.rb
+++ b/activerecord/lib/active_record/associations/association_scope.rb
@@ -46,13 +46,9 @@ module ActiveRecord
         binds
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :value_transformation
 
-      private
         def join(table, constraint)
           table.create_join(table, table.create_on(constraint))
         end
@@ -135,7 +131,7 @@ module ActiveRecord
               item = eval_scope(reflection, scope_chain_item, owner)
 
               if scope_chain_item == chain_head.scope
-                scope.merge! item.except(:where, :includes)
+                scope.merge! item.except(:where, :includes, :unscope, :order)
               end
 
               reflection.all_includes do
@@ -144,7 +140,7 @@ module ActiveRecord
 
               scope.unscope!(*item.unscope_values)
               scope.where_clause += item.where_clause
-              scope.order_values |= item.order_values
+              scope.order_values = item.order_values | scope.order_values
             end
           end
 
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index de8afc9ccb..443ccaaa72 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -53,7 +53,7 @@ module ActiveRecord
       # Implements the ids writer method, e.g. foo.item_ids= for Foo.has_many :items
       def ids_writer(ids)
         primary_key = reflection.association_primary_key
-        pk_type = klass.type_for_attribute(primary_key.to_s)
+        pk_type = klass.type_for_attribute(primary_key)
         ids = Array(ids).reject(&:blank?)
         ids.map! { |i| pk_type.cast(i) }
 
diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 8b4a48a38c..9a30198b95 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -32,7 +32,7 @@ module ActiveRecord
     class CollectionProxy < Relation
       def initialize(klass, association) #:nodoc:
         @association = association
-        super klass, klass.arel_table, klass.predicate_builder
+        super klass
 
         extensions = association.extensions
         extend(*extensions) if extensions.any?
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 7a3bef969b..59929b8c4e 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -8,9 +8,7 @@ module ActiveRecord
 
       def initialize(owner, reflection)
         super
-
-        @through_records     = {}
-        @through_association = nil
+        @through_records = {}
       end
 
       def concat(*records)
@@ -50,11 +48,6 @@ module ActiveRecord
       end
 
       private
-
-        def through_association
-          @through_association ||= owner.association(through_reflection.name)
-        end
-
         # The through record (built with build_record) is temporarily cached
         # so that it may be reused if insert_record is subsequently called.
         #
@@ -145,7 +138,7 @@ module ActiveRecord
           case method
           when :destroy
             if scope.klass.primary_key
-              count = scope.destroy_all.length
+              count = scope.destroy_all.count(&:destroyed?)
             else
               scope.each(&:_run_destroy_callbacks)
               count = scope.delete_all
diff --git a/activerecord/lib/active_record/associations/has_one_through_association.rb b/activerecord/lib/active_record/associations/has_one_through_association.rb
index 36746f9115..491282adf7 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -6,17 +6,16 @@ module ActiveRecord
     class HasOneThroughAssociation < HasOneAssociation #:nodoc:
       include ThroughAssociation
 
-      def replace(record)
-        create_through_record(record)
+      def replace(record, save = true)
+        create_through_record(record, save)
         self.target = record
       end
 
       private
-
-        def create_through_record(record)
+        def create_through_record(record, save)
           ensure_not_nested
 
-          through_proxy  = owner.association(through_reflection.name)
+          through_proxy  = through_association
           through_record = through_proxy.load_target
 
           if through_record && !record
@@ -30,7 +29,7 @@ module ActiveRecord
 
             if through_record
               through_record.update(attributes)
-            elsif owner.new_record?
+            elsif owner.new_record? || !save
               through_proxy.build(attributes)
             else
               through_proxy.create(attributes)
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index 221c791bf8..c36386ec7e 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -58,7 +58,7 @@ module ActiveRecord
           tables.first
         end
 
-        protected
+        private
           attr_reader :alias_tracker
       end
     end
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb
index 59320431ee..1ea0aeac3a 100644
--- a/activerecord/lib/active_record/associations/preloader.rb
+++ b/activerecord/lib/active_record/associations/preloader.rb
@@ -169,7 +169,7 @@ module ActiveRecord
             owners.flat_map { |owner| owner.association(reflection.name).target }
           end
 
-          protected
+          private
             attr_reader :owners, :reflection
         end
 
diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index 735da152b7..ddcad4504c 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -27,10 +27,9 @@ module ActiveRecord
           end
         end
 
-        protected
+        private
           attr_reader :owners, :reflection, :preload_scope, :model, :klass
 
-        private
           # The name of the key on the associated records
           def association_key_name
             reflection.join_primary_key(klass)
@@ -82,11 +81,11 @@ module ActiveRecord
           end
 
           def association_key_type
-            @klass.type_for_attribute(association_key_name.to_s).type
+            @klass.type_for_attribute(association_key_name).type
           end
 
           def owner_key_type
-            @model.type_for_attribute(owner_key_name.to_s).type
+            @model.type_for_attribute(owner_key_name).type
           end
 
           def load_records(&block)
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index 54673b74f7..5afb0bc068 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -19,6 +19,10 @@ module ActiveRecord
           end
         end
 
+        def through_association
+          @through_association ||= owner.association(through_reflection.name)
+        end
+
         # We merge in these scopes for two reasons:
         #
         #   1. To get the default_scope conditions for any of the other reflections in the chain
diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index 64f81ca582..842f407517 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -432,15 +432,12 @@ module ActiveRecord
       @attributes.accessed
     end
 
-    protected
-
-      def attribute_method?(attr_name) # :nodoc:
+    private
+      def attribute_method?(attr_name)
         # We check defined? because Syck calls respond_to? before actually calling initialize.
         defined?(@attributes) && @attributes.key?(attr_name)
       end
 
-    private
-
       def arel_attributes_with_values_for_create(attribute_names)
         arel_attributes_with_values(attributes_for_create(attribute_names))
       end
@@ -456,7 +453,7 @@ module ActiveRecord
         arel_table = self.class.arel_table
 
         attribute_names.each do |name|
-          attrs[arel_table[name]] = typecasted_attribute_value(name)
+          attrs[arel_table[name]] = _read_attribute(name)
         end
         attrs
       end
@@ -483,9 +480,5 @@ module ActiveRecord
       def pk_attribute?(name)
         name == self.class.primary_key
       end
-
-      def typecasted_attribute_value(name)
-        _read_attribute(name)
-      end
   end
 end
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index 3de6fe566d..df4c79b0f6 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -32,9 +32,7 @@ module ActiveRecord
       # <tt>reload</tt> the record and clears changed attributes.
       def reload(*)
         super.tap do
-          @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
           @mutations_before_last_save = nil
-          @attributes_changed_by_setter = ActiveSupport::HashWithIndifferentAccess.new
           @mutations_from_database = nil
         end
       end
@@ -114,12 +112,12 @@ module ActiveRecord
 
       # Alias for +changed+
       def changed_attribute_names_to_save
-        changes_to_save.keys
+        mutations_from_database.changed_attribute_names
       end
 
       # Alias for +changed_attributes+
       def attributes_in_database
-        changes_to_save.transform_values(&:first)
+        mutations_from_database.changed_values
       end
 
       private
diff --git a/activerecord/lib/active_record/attribute_methods/primary_key.rb b/activerecord/lib/active_record/attribute_methods/primary_key.rb
index d8fc046e10..2907547634 100644
--- a/activerecord/lib/active_record/attribute_methods/primary_key.rb
+++ b/activerecord/lib/active_record/attribute_methods/primary_key.rb
@@ -131,7 +131,7 @@ module ActiveRecord
             def suppress_composite_primary_key(pk)
               return pk unless pk.is_a?(Array)
 
-              warn <<-WARNING.strip_heredoc
+              warn <<~WARNING
                 WARNING: Active Record does not support composite primary key.
 
                 #{table_name} has composite primary key. Composite primary key is ignored.
diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index ebc2baed34..6e0e90f39c 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -7,7 +7,7 @@ module ActiveRecord
 
       class ColumnNotSerializableError < StandardError
         def initialize(name, type)
-          super <<-EOS.strip_heredoc
+          super <<~EOS
             Column `#{name}` of type #{type.class} does not support `serialize` feature.
             Usually it means that you are trying to use `serialize`
             on a column that already implements serialization natively.
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index b7ad944cec..cc99401390 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -9,7 +9,6 @@ require "active_support/core_ext/module/attribute_accessors"
 require "active_support/core_ext/array/extract_options"
 require "active_support/core_ext/hash/deep_merge"
 require "active_support/core_ext/hash/slice"
-require "active_support/core_ext/hash/transform_values"
 require "active_support/core_ext/string/behavior"
 require "active_support/core_ext/kernel/singleton_class"
 require "active_support/core_ext/module/introspection"
diff --git a/activerecord/lib/active_record/collection_cache_key.rb b/activerecord/lib/active_record/collection_cache_key.rb
index 0520591f4f..dfba78614e 100644
--- a/activerecord/lib/active_record/collection_cache_key.rb
+++ b/activerecord/lib/active_record/collection_cache_key.rb
@@ -15,7 +15,7 @@ module ActiveRecord
         if collection.eager_loading?
           collection = collection.send(:apply_join_dependency)
         end
-        column_type = type_for_attribute(timestamp_column.to_s)
+        column_type = type_for_attribute(timestamp_column)
         column = connection.column_name_from_arel_node(collection.arel_attribute(timestamp_column))
         select_values = "COUNT(*) AS #{connection.quote_column_name("size")}, MAX(%s) AS timestamp"
 
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
index 36048bee03..08f3e15a4b 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb
@@ -356,35 +356,33 @@ module ActiveRecord
       # Inserts a set of fixtures into the table. Overridden in adapters that require
       # something beyond a simple insert (eg. Oracle).
       def insert_fixtures(fixtures, table_name)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          `insert_fixtures` is deprecated and will be removed in the next version of Rails.
+          Consider using `insert_fixtures_set` for performance improvement.
+        MSG
         return if fixtures.empty?
 
-        columns = schema_cache.columns_hash(table_name)
+        execute(build_fixture_sql(fixtures, table_name), "Fixtures Insert")
+      end
 
-        values = fixtures.map do |fixture|
-          fixture = fixture.stringify_keys
+      def insert_fixtures_set(fixture_set, tables_to_delete = [])
+        fixture_inserts = fixture_set.map do |table_name, fixtures|
+          next if fixtures.empty?
 
-          unknown_columns = fixture.keys - columns.keys
-          if unknown_columns.any?
-            raise Fixture::FixtureError, %(table "#{table_name}" has no columns named #{unknown_columns.map(&:inspect).join(', ')}.)
-          end
+          build_fixture_sql(fixtures, table_name)
+        end.compact
 
-          columns.map do |name, column|
-            if fixture.key?(name)
-              type = lookup_cast_type_from_column(column)
-              bind = Relation::QueryAttribute.new(name, fixture[name], type)
-              with_yaml_fallback(bind.value_for_database)
-            else
-              Arel.sql("DEFAULT")
+        table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name table}".dup }
+        total_sql = Array.wrap(combine_multi_statements(table_deletes + fixture_inserts))
+
+        disable_referential_integrity do
+          transaction(requires_new: true) do
+            total_sql.each do |sql|
+              execute sql, "Fixtures Load"
+              yield if block_given?
             end
           end
         end
-
-        table = Arel::Table.new(table_name)
-        manager = Arel::InsertManager.new
-        manager.into(table)
-        columns.each_key { |column| manager.columns << table[column] }
-        manager.values = manager.create_values_list(values)
-        execute manager.to_sql, "Fixtures Insert"
       end
 
       def empty_insert_statement_value
@@ -416,6 +414,44 @@ module ActiveRecord
       alias join_to_delete join_to_update
 
       private
+        def default_insert_value(column)
+          Arel.sql("DEFAULT")
+        end
+
+        def build_fixture_sql(fixtures, table_name)
+          columns = schema_cache.columns_hash(table_name)
+
+          values = fixtures.map do |fixture|
+            fixture = fixture.stringify_keys
+
+            unknown_columns = fixture.keys - columns.keys
+            if unknown_columns.any?
+              raise Fixture::FixtureError, %(table "#{table_name}" has no columns named #{unknown_columns.map(&:inspect).join(', ')}.)
+            end
+
+            columns.map do |name, column|
+              if fixture.key?(name)
+                type = lookup_cast_type_from_column(column)
+                bind = Relation::QueryAttribute.new(name, fixture[name], type)
+                with_yaml_fallback(bind.value_for_database)
+              else
+                default_insert_value(column)
+              end
+            end
+          end
+
+          table = Arel::Table.new(table_name)
+          manager = Arel::InsertManager.new
+          manager.into(table)
+          columns.each_key { |column| manager.columns << table[column] }
+          manager.values = manager.create_values_list(values)
+
+          manager.to_sql
+        end
+
+        def combine_multi_statements(total_sql)
+          total_sql.join(";\n")
+        end
 
         # Returns a subquery for the given key using the join information.
         def subquery_for(key, select)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
index 4a191d337c..22abdee4b8 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require "active_support/core_ext/string/strip"
-
 module ActiveRecord
   module ConnectionAdapters
     class AbstractAdapter
@@ -66,7 +64,7 @@ module ActiveRecord
           end
 
           def visit_ForeignKeyDefinition(o)
-            sql = <<-SQL.strip_heredoc
+            sql = +<<~SQL
               CONSTRAINT #{quote_column_name(o.name)}
               FOREIGN KEY (#{quote_column_name(o.column)})
                 REFERENCES #{quote_table_name(o.to_table)} (#{quote_column_name(o.primary_key)})
@@ -133,7 +131,7 @@ module ActiveRecord
             when :cascade  then "ON #{action} CASCADE"
             when :restrict then "ON #{action} RESTRICT"
             else
-              raise ArgumentError, <<-MSG.strip_heredoc
+              raise ArgumentError, <<~MSG
                 '#{dependency}' is not supported for :on_update or :on_delete.
                 Supported values are: :nullify, :cascade, :restrict
               MSG
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 0594b4b485..584a86da21 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -151,13 +151,8 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :name, :polymorphic, :index, :foreign_key, :type, :options
-
       private
+        attr_reader :name, :polymorphic, :index, :foreign_key, :type, :options
 
         def as_options(value)
           value.is_a?(Hash) ? value : {}
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 4f58b0242c..db033db913 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -715,7 +715,7 @@ module ActiveRecord
       #
       #   CREATE INDEX by_branch_desc_party ON accounts(branch_id DESC, party_id ASC, surname)
       #
-      # Note: MySQL doesn't yet support index order (it accepts the syntax but ignores it).
+      # Note: MySQL only supports index order from 8.0.1 onwards (earlier versions accepted the syntax but ignored it).
       #
       # ====== Creating a partial index
       #
@@ -1049,8 +1049,8 @@ module ActiveRecord
         sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name)
 
         migrated = ActiveRecord::SchemaMigration.all_versions.map(&:to_i)
-        versions = ActiveRecord::Migrator.migration_files(migrations_paths).map do |file|
-          ActiveRecord::Migrator.parse_migration_filename(file).first.to_i
+        versions = migration_context.migration_files.map do |file|
+          migration_context.parse_migration_filename(file).first.to_i
         end
 
         unless migrated.include?(version)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 2655407d75..559f068c39 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -119,6 +119,14 @@ module ActiveRecord
         end
       end
 
+      def migrations_paths # :nodoc:
+        @config[:migrations_paths] || Migrator.migrations_paths
+      end
+
+      def migration_context # :nodoc:
+        MigrationContext.new(migrations_paths)
+      end
+
       class Version
         include Comparable
 
@@ -318,6 +326,11 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support foreign/external tables?
+      def supports_foreign_tables?
+        false
+      end
+
       # This is meant to be implemented by the adapters that support extensions
       def disable_extension(name)
       end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index b394a8969f..608258d05c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -11,8 +11,6 @@ require "active_record/connection_adapters/mysql/schema_dumper"
 require "active_record/connection_adapters/mysql/schema_statements"
 require "active_record/connection_adapters/mysql/type_metadata"
 
-require "active_support/core_ext/string/strip"
-
 module ActiveRecord
   module ConnectionAdapters
     class AbstractMysqlAdapter < AbstractAdapter
@@ -284,7 +282,7 @@ module ActiveRecord
       def table_comment(table_name) # :nodoc:
         scope = quoted_scope(table_name)
 
-        query_value(<<-SQL.strip_heredoc, "SCHEMA").presence
+        query_value(<<~SQL, "SCHEMA").presence
           SELECT table_comment
           FROM information_schema.tables
           WHERE table_schema = #{scope[:schema]}
@@ -392,7 +390,7 @@ module ActiveRecord
 
         scope = quoted_scope(table_name)
 
-        fk_info = exec_query(<<-SQL.strip_heredoc, "SCHEMA")
+        fk_info = exec_query(<<~SQL, "SCHEMA")
           SELECT fk.referenced_table_name AS 'to_table',
                  fk.referenced_column_name AS 'primary_key',
                  fk.column_name AS 'column',
@@ -480,7 +478,7 @@ module ActiveRecord
 
         scope = quoted_scope(table_name)
 
-        query_values(<<-SQL.strip_heredoc, "SCHEMA")
+        query_values(<<~SQL, "SCHEMA")
           SELECT column_name
           FROM information_schema.key_column_usage
           WHERE constraint_name = 'PRIMARY'
@@ -526,23 +524,49 @@ module ActiveRecord
         index.using == :btree || super
       end
 
-      def insert_fixtures(*)
-        without_sql_mode("NO_AUTO_VALUE_ON_ZERO") { super }
+      def insert_fixtures_set(fixture_set, tables_to_delete = [])
+        with_multi_statements do
+          super { discard_remaining_results }
+        end
       end
 
       private
+        def combine_multi_statements(total_sql)
+          total_sql.each_with_object([]) do |sql, total_sql_chunks|
+            previous_packet = total_sql_chunks.last
+            sql << ";\n"
+            if max_allowed_packet_reached?(sql, previous_packet) || total_sql_chunks.empty?
+              total_sql_chunks << sql
+            else
+              previous_packet << sql
+            end
+          end
+        end
+
+        def max_allowed_packet_reached?(current_packet, previous_packet)
+          if current_packet.bytesize > max_allowed_packet
+            raise ActiveRecordError, "Fixtures set is too large #{current_packet.bytesize}. Consider increasing the max_allowed_packet variable."
+          elsif previous_packet.nil?
+            false
+          else
+            (current_packet.bytesize + previous_packet.bytesize) > max_allowed_packet
+          end
+        end
+
+        def max_allowed_packet
+          bytes_margin = 2
+          @max_allowed_packet ||= (show_variable("max_allowed_packet") - bytes_margin)
+        end
 
-        def without_sql_mode(mode)
-          result = execute("SELECT @@SESSION.sql_mode")
-          current_mode = result.first[0]
-          return yield unless current_mode.include?(mode)
+        def with_multi_statements
+          previous_flags = @config[:flags]
+          @config[:flags] = Mysql2::Client::MULTI_STATEMENTS
+          reconnect!
 
-          sql_mode = "REPLACE(@@sql_mode, '#{mode}', '')"
-          execute("SET @@SESSION.sql_mode = #{sql_mode}")
           yield
         ensure
-          sql_mode = "CONCAT(@@sql_mode, ',#{mode}')"
-          execute("SET @@SESSION.sql_mode = #{sql_mode}")
+          @config[:flags] = previous_flags
+          reconnect!
         end
 
         def initialize_type_map(m = type_map)
diff --git a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
index a058a72872..458c9bfd70 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql/database_statements.rb
@@ -11,7 +11,7 @@ module ActiveRecord
           else
             super
           end
-          @connection.next_result while @connection.more_results?
+          discard_remaining_results
           result
         end
 
@@ -50,11 +50,18 @@ module ActiveRecord
         alias :exec_update :exec_delete
 
         private
+          def default_insert_value(column)
+            Arel.sql("DEFAULT") unless column.auto_increment?
+          end
 
           def last_inserted_id(result)
             @connection.last_id
           end
 
+          def discard_remaining_results
+            @connection.abandon_results!
+          end
+
           def exec_stmt_and_free(sql, name, binds, cache_stmt: false)
             # make sure we carry over any changes to ActiveRecord::Base.default_timezone that have been
             # made since we established the connection
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
index 469ef3f5a0..3ccc7271ab 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/column.rb
@@ -20,10 +20,9 @@ module ActiveRecord
         end
       end
 
-      protected
+      private
         attr_reader :max_identifier_length
 
-      private
         def sequence_name_from_parts(table_name, column_name, suffix)
           over_length = [table_name, column_name, suffix].map(&:length).sum + 2 - max_identifier_length
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
index 542ca75d3e..247a25054e 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid.rb
@@ -5,6 +5,7 @@ require "active_record/connection_adapters/postgresql/oid/bit"
 require "active_record/connection_adapters/postgresql/oid/bit_varying"
 require "active_record/connection_adapters/postgresql/oid/bytea"
 require "active_record/connection_adapters/postgresql/oid/cidr"
+require "active_record/connection_adapters/postgresql/oid/date"
 require "active_record/connection_adapters/postgresql/oid/date_time"
 require "active_record/connection_adapters/postgresql/oid/decimal"
 require "active_record/connection_adapters/postgresql/oid/enum"
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
index 587e95d192..e9a79526f9 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/bit.rb
@@ -43,10 +43,7 @@ module ActiveRecord
               /\A[0-9A-F]*\Z/i.match?(value)
             end
 
-            # TODO Change this to private once we've dropped Ruby 2.2 support.
-            # Workaround for Ruby 2.2 "private attribute?" warning.
-            protected
-
+            private
               attr_reader :value
           end
         end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/date.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date.rb
new file mode 100644
index 0000000000..24a1daa95a
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/date.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module ActiveRecord
+  module ConnectionAdapters
+    module PostgreSQL
+      module OID # :nodoc:
+        class Date < Type::Date # :nodoc:
+          def cast_value(value)
+            case value
+            when "infinity" then ::Float::INFINITY
+            when "-infinity" then -::Float::INFINITY
+            when / BC$/
+              astronomical_year = format("%04d", -value[/^\d+/].to_i + 1)
+              super(value.sub(/ BC$/, "").sub(/^\d+/, astronomical_year))
+            else
+              super
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index a8895f8606..6f3db772cd 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -38,7 +38,7 @@ module ActiveRecord
                       " TABLESPACE = \"#{value}\""
                     when :connection_limit
                       " CONNECTION LIMIT = #{value}"
-            else
+                    else
                       ""
             end
           end
@@ -115,7 +115,7 @@ module ActiveRecord
             if indkey.include?(0)
               columns = expressions
             else
-              columns = Hash[query(<<-SQL.strip_heredoc, "SCHEMA")].values_at(*indkey).compact
+              columns = Hash[query(<<~SQL, "SCHEMA")].values_at(*indkey).compact
                 SELECT a.attnum, a.attname
                 FROM pg_attribute a
                 WHERE a.attrelid = #{oid}
@@ -124,9 +124,13 @@ module ActiveRecord
 
               # add info on sort order (only desc order is explicitly specified, asc is the default)
               # and non-default opclasses
-              expressions.scan(/(\w+)(?: (?!DESC)(\w+))?(?: (DESC))?/).each do |column, opclass, desc|
+              expressions.scan(/(?<column>\w+)\s?(?<opclass>\w+_ops)?\s?(?<desc>DESC)?\s?(?<nulls>NULLS (?:FIRST|LAST))?/).each do |column, opclass, desc, nulls|
                 opclasses[column] = opclass.to_sym if opclass
-                orders[column] = :desc if desc
+                if nulls
+                  orders[column] = [desc, nulls].compact.join(" ")
+                else
+                  orders[column] = :desc if desc
+                end
               end
             end
 
@@ -154,7 +158,7 @@ module ActiveRecord
         def table_comment(table_name) # :nodoc:
           scope = quoted_scope(table_name, type: "BASE TABLE")
           if scope[:name]
-            query_value(<<-SQL.strip_heredoc, "SCHEMA")
+            query_value(<<~SQL, "SCHEMA")
               SELECT pg_catalog.obj_description(c.oid, 'pg_class')
               FROM pg_catalog.pg_class c
                 LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
@@ -349,7 +353,7 @@ module ActiveRecord
         end
 
         def primary_keys(table_name) # :nodoc:
-          query_values(<<-SQL.strip_heredoc, "SCHEMA")
+          query_values(<<~SQL, "SCHEMA")
             SELECT a.attname
               FROM (
                      SELECT indrelid, indkey, generate_subscripts(indkey, 1) idx
@@ -375,7 +379,7 @@ module ActiveRecord
             if respond_to?(method, true)
               sqls, procs = Array(send(method, table, *arguments)).partition { |v| v.is_a?(String) }
               sql_fragments << sqls
-              non_combinable_operations << procs if procs.present?
+              non_combinable_operations.concat(procs)
             else
               execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
               non_combinable_operations.each(&:call)
@@ -498,7 +502,7 @@ module ActiveRecord
 
         def foreign_keys(table_name)
           scope = quoted_scope(table_name)
-          fk_info = exec_query(<<-SQL.strip_heredoc, "SCHEMA")
+          fk_info = exec_query(<<~SQL, "SCHEMA")
             SELECT t2.oid::regclass::text AS to_table, a1.attname AS column, a2.attname AS primary_key, c.conname AS name, c.confupdtype AS on_update, c.confdeltype AS on_delete, c.convalidated AS valid
             FROM pg_constraint c
             JOIN pg_class t1 ON c.conrelid = t1.oid
@@ -527,6 +531,14 @@ module ActiveRecord
           end
         end
 
+        def foreign_tables
+          query_values(data_source_sql(type: "FOREIGN TABLE"), "SCHEMA")
+        end
+
+        def foreign_table_exists?(table_name)
+          query_values(data_source_sql(table_name, type: "FOREIGN TABLE"), "SCHEMA").any? if table_name.present?
+        end
+
         # Maps logical Rails types to PostgreSQL-specific data types.
         def type_to_sql(type, limit: nil, precision: nil, scale: nil, array: nil, **) # :nodoc:
           sql = \
@@ -739,7 +751,7 @@ module ActiveRecord
 
           def data_source_sql(name = nil, type: nil)
             scope = quoted_scope(name, type: type)
-            scope[:type] ||= "'r','v','m'" # (r)elation/table, (v)iew, (m)aterialized view
+            scope[:type] ||= "'r','v','m','f'" # (r)elation/table, (v)iew, (m)aterialized view, (f)oreign table
 
             sql = "SELECT c.relname FROM pg_class c LEFT JOIN pg_namespace n ON n.oid = c.relnamespace".dup
             sql << " WHERE n.nspname = #{scope[:schema]}"
@@ -756,6 +768,8 @@ module ActiveRecord
                 "'r'"
               when "VIEW"
                 "'v','m'"
+              when "FOREIGN TABLE"
+                "'f'"
               end
             scope = {}
             scope[:schema] = schema ? quote(schema) : "ANY (current_schemas(false))"
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 9ac5a8760e..fdf6f75108 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -281,7 +281,7 @@ module ActiveRecord
       end
 
       def discard! # :nodoc:
-        @connection.socket_io.reopen(IO::NULL)
+        @connection.socket_io.reopen(IO::NULL) rescue nil
         @connection = nil
       end
 
@@ -318,6 +318,10 @@ module ActiveRecord
         postgresql_version >= 90300
       end
 
+      def supports_foreign_tables?
+        postgresql_version >= 90300
+      end
+
       def supports_pgcrypto_uuid?
         postgresql_version >= 90400
       end
@@ -461,7 +465,7 @@ module ActiveRecord
           register_class_with_limit m, "bit", OID::Bit
           register_class_with_limit m, "varbit", OID::BitVarying
           m.alias_type "timestamptz", "timestamp"
-          m.register_type "date", Type::Date.new
+          m.register_type "date", OID::Date.new
 
           m.register_type "money", OID::Money.new
           m.register_type "bytea", OID::Bytea.new
@@ -833,6 +837,7 @@ module ActiveRecord
         ActiveRecord::Type.register(:bit_varying, OID::BitVarying, adapter: :postgresql)
         ActiveRecord::Type.register(:binary, OID::Bytea, adapter: :postgresql)
         ActiveRecord::Type.register(:cidr, OID::Cidr, adapter: :postgresql)
+        ActiveRecord::Type.register(:date, OID::Date, adapter: :postgresql)
         ActiveRecord::Type.register(:datetime, OID::DateTime, adapter: :postgresql)
         ActiveRecord::Type.register(:decimal, OID::Decimal, adapter: :postgresql)
         ActiveRecord::Type.register(:enum, OID::Enum, adapter: :postgresql)
diff --git a/activerecord/lib/active_record/connection_adapters/schema_cache.rb b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
index f34b6733da..c29cf1f9a1 100644
--- a/activerecord/lib/active_record/connection_adapters/schema_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/schema_cache.rb
@@ -28,7 +28,7 @@ module ActiveRecord
         coder["columns_hash"] = @columns_hash
         coder["primary_keys"] = @primary_keys
         coder["data_sources"] = @data_sources
-        coder["version"] = ActiveRecord::Migrator.current_version
+        coder["version"] = connection.migration_context.current_version
       end
 
       def init_with(coder)
@@ -100,7 +100,7 @@ module ActiveRecord
 
       def marshal_dump
         # if we get current version during initialization, it happens stack over flow.
-        @version = ActiveRecord::Migrator.current_version
+        @version = connection.migration_context.current_version
         [@version, @columns, @columns_hash, @primary_keys, @data_sources]
       end
 
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
index d4f5bd16ac..a958600446 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
@@ -101,7 +101,7 @@ module ActiveRecord
       def initialize(connection, logger, connection_options, config)
         super(connection, logger, config)
 
-        @active     = nil
+        @active     = true
         @statements = StatementPool.new(self.class.type_cast_config_to_integer(config[:statement_limit]))
 
         configure_connection
@@ -144,7 +144,7 @@ module ActiveRecord
       end
 
       def active?
-        @active != false
+        @active
       end
 
       # Disconnects from the database if already connected. Otherwise, this
@@ -367,8 +367,22 @@ module ActiveRecord
       end
 
       def insert_fixtures(rows, table_name)
-        rows.each do |row|
-          insert_fixture(row, table_name)
+        ActiveSupport::Deprecation.warn(<<-MSG.squish)
+          `insert_fixtures` is deprecated and will be removed in the next version of Rails.
+          Consider using `insert_fixtures_set` for performance improvement.
+        MSG
+        insert_fixtures_set(table_name => rows)
+      end
+
+      def insert_fixtures_set(fixture_set, tables_to_delete = [])
+        disable_referential_integrity do
+          transaction(requires_new: true) do
+            tables_to_delete.each { |table| delete "DELETE FROM #{quote_table_name(table)}", "Fixture Delete" }
+
+            fixture_set.each do |table_name, rows|
+              rows.each { |row| insert_fixture(row, table_name) }
+            end
+          end
         end
       end
 
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 88810cb328..e1a0b2ecf8 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -281,7 +281,7 @@ module ActiveRecord
         end
 
         def relation
-          relation = Relation.create(self, arel_table, predicate_builder)
+          relation = Relation.create(self)
 
           if finder_needs_type_condition? && !ignore_default_scope?
             relation.where!(type_condition)
@@ -382,8 +382,10 @@ module ActiveRecord
 
       _run_initialize_callbacks
 
-      @new_record  = true
-      @destroyed   = false
+      @new_record               = true
+      @destroyed                = false
+      @_start_transaction_state = {}
+      @transaction_state        = nil
 
       super
     end
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index 1a3e6e4d09..23ecb24542 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -141,10 +141,7 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :name, :mapping, :subtype
     end
 
diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index efcbd44776..c2a180c939 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -120,13 +120,13 @@ module ActiveRecord
     def initialize(adapter = nil, message: nil, table: nil, foreign_key: nil, target_table: nil, primary_key: nil)
       @adapter = adapter
       if table
-        msg = <<-EOM.strip_heredoc
+        msg = +<<~EOM
           Column `#{foreign_key}` on table `#{table}` has a type of `#{column_type(table, foreign_key)}`.
           This does not match column `#{primary_key}` on `#{target_table}`, which has type `#{column_type(target_table, primary_key)}`.
           To resolve this issue, change the type of the `#{foreign_key}` column on `#{table}` to be :integer. (For example `t.integer #{foreign_key}`).
         EOM
       else
-        msg = <<-EOM
+        msg = +<<~EOM
           There is a mismatch between the foreign key and primary key column types.
           Verify that the foreign key column type and the primary key of the associated table match types.
         EOM
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index 86f13d75d5..8f022ff7a7 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -169,13 +169,13 @@ module ActiveRecord
   #     self.use_transactional_tests = true
   #
   #     test "godzilla" do
-  #       assert !Foo.all.empty?
+  #       assert_not_empty Foo.all
   #       Foo.destroy_all
-  #       assert Foo.all.empty?
+  #       assert_empty Foo.all
   #     end
   #
   #     test "godzilla aftermath" do
-  #       assert !Foo.all.empty?
+  #       assert_not_empty Foo.all
   #     end
   #   end
   #
@@ -540,47 +540,38 @@ module ActiveRecord
       }
 
       unless files_to_read.empty?
-        connection.disable_referential_integrity do
-          fixtures_map = {}
-
-          fixture_sets = files_to_read.map do |fs_name|
-            klass = class_names[fs_name]
-            conn = klass ? klass.connection : connection
-            fixtures_map[fs_name] = new( # ActiveRecord::FixtureSet.new
-              conn,
-              fs_name,
-              klass,
-              ::File.join(fixtures_directory, fs_name))
-          end
-
-          update_all_loaded_fixtures fixtures_map
-
-          connection.transaction(requires_new: true) do
-            deleted_tables = Hash.new { |h, k| h[k] = Set.new }
-            fixture_sets.each do |fs|
-              conn = fs.model_class.respond_to?(:connection) ? fs.model_class.connection : connection
-              table_rows = fs.table_rows
+        fixtures_map = {}
+
+        fixture_sets = files_to_read.map do |fs_name|
+          klass = class_names[fs_name]
+          conn = klass ? klass.connection : connection
+          fixtures_map[fs_name] = new( # ActiveRecord::FixtureSet.new
+            conn,
+            fs_name,
+            klass,
+            ::File.join(fixtures_directory, fs_name))
+        end
 
-              table_rows.each_key do |table|
-                unless deleted_tables[conn].include? table
-                  conn.delete "DELETE FROM #{conn.quote_table_name(table)}", "Fixture Delete"
-                end
-                deleted_tables[conn] << table
-              end
+        update_all_loaded_fixtures fixtures_map
+        fixture_sets_by_connection = fixture_sets.group_by { |fs| fs.model_class ? fs.model_class.connection : connection }
 
-              table_rows.each do |fixture_set_name, rows|
-                conn.insert_fixtures(rows, fixture_set_name)
-              end
+        fixture_sets_by_connection.each do |conn, set|
+          table_rows_for_connection = Hash.new { |h, k| h[k] = [] }
 
-              # Cap primary key sequences to max(pk).
-              if conn.respond_to?(:reset_pk_sequence!)
-                conn.reset_pk_sequence!(fs.table_name)
-              end
+          set.each do |fs|
+            fs.table_rows.each do |table, rows|
+              table_rows_for_connection[table].unshift(*rows)
             end
           end
+          conn.insert_fixtures_set(table_rows_for_connection, table_rows_for_connection.keys)
 
-          cache_fixtures(connection, fixtures_map)
+          # Cap primary key sequences to max(pk).
+          if conn.respond_to?(:reset_pk_sequence!)
+            set.each { |fs| conn.reset_pk_sequence!(fs.table_name) }
+          end
         end
+
+        cache_fixtures(connection, fixtures_map)
       end
       cached_fixtures(connection, fixture_set_names)
     end
@@ -883,6 +874,7 @@ module ActiveRecord
       class_attribute :use_instantiated_fixtures, default: false # true, false, or :no_instances
       class_attribute :pre_loaded_fixtures, default: false
       class_attribute :config, default: ActiveRecord::Base
+      class_attribute :lock_threads, default: true
     end
 
     module ClassMethods
@@ -982,7 +974,7 @@ module ActiveRecord
         @fixture_connections = enlist_fixture_connections
         @fixture_connections.each do |connection|
           connection.begin_transaction joinable: false
-          connection.pool.lock_thread = true
+          connection.pool.lock_thread = true if lock_threads
         end
 
         # When connections are established in the future, begin a transaction too
@@ -998,7 +990,7 @@ module ActiveRecord
 
             if connection && !@fixture_connections.include?(connection)
               connection.begin_transaction joinable: false
-              connection.pool.lock_thread = true
+              connection.pool.lock_thread = true if lock_threads
               @fixture_connections << connection
             end
           end
diff --git a/activerecord/lib/active_record/gem_version.rb b/activerecord/lib/active_record/gem_version.rb
index 7e47dac016..72035a986b 100644
--- a/activerecord/lib/active_record/gem_version.rb
+++ b/activerecord/lib/active_record/gem_version.rb
@@ -7,10 +7,10 @@ module ActiveRecord
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activerecord/lib/active_record/internal_metadata.rb b/activerecord/lib/active_record/internal_metadata.rb
index 5a65edf27e..3626a13d7c 100644
--- a/activerecord/lib/active_record/internal_metadata.rb
+++ b/activerecord/lib/active_record/internal_metadata.rb
@@ -17,7 +17,7 @@ module ActiveRecord
       end
 
       def []=(key, value)
-        find_or_initialize_by(key: key).update_attributes!(value: value)
+        find_or_initialize_by(key: key).update!(value: value)
       end
 
       def [](key)
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index f6648a4e3d..5322571820 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -550,7 +550,7 @@ module ActiveRecord
       end
 
       def call(env)
-        mtime = ActiveRecord::Migrator.last_migration.mtime.to_i
+        mtime = ActiveRecord::Base.connection.migration_context.last_migration.mtime.to_i
         if @last_check < mtime
           ActiveRecord::Migration.check_pending!(connection)
           @last_check = mtime
@@ -575,11 +575,11 @@ module ActiveRecord
 
       # Raises <tt>ActiveRecord::PendingMigrationError</tt> error if any migrations are pending.
       def check_pending!(connection = Base.connection)
-        raise ActiveRecord::PendingMigrationError if ActiveRecord::Migrator.needs_migration?(connection)
+        raise ActiveRecord::PendingMigrationError if connection.migration_context.needs_migration?
       end
 
       def load_schema_if_pending!
-        if ActiveRecord::Migrator.needs_migration? || !ActiveRecord::Migrator.any_migrations?
+        if Base.connection.migration_context.needs_migration? || !Base.connection.migration_context.any_migrations?
           # Roundtrip to Rake to allow plugins to hook into database initialization.
           root = defined?(ENGINE_ROOT) ? ENGINE_ROOT : Rails.root
           FileUtils.cd(root) do
@@ -876,10 +876,10 @@ module ActiveRecord
 
       FileUtils.mkdir_p(destination) unless File.exist?(destination)
 
-      destination_migrations = ActiveRecord::Migrator.migrations(destination)
+      destination_migrations = ActiveRecord::MigrationContext.new(destination).migrations
       last = destination_migrations.last
       sources.each do |scope, path|
-        source_migrations = ActiveRecord::Migrator.migrations(path)
+        source_migrations = ActiveRecord::MigrationContext.new(path).migrations
 
         source_migrations.each do |migration|
           source = File.binread(migration.filename)
@@ -997,132 +997,147 @@ module ActiveRecord
     end
   end
 
-  class Migrator#:nodoc:
-    class << self
-      attr_writer :migrations_paths
-      alias :migrations_path= :migrations_paths=
-
-      def migrate(migrations_paths, target_version = nil, &block)
-        case
-        when target_version.nil?
-          up(migrations_paths, target_version, &block)
-        when current_version == 0 && target_version == 0
-          []
-        when current_version > target_version
-          down(migrations_paths, target_version, &block)
-        else
-          up(migrations_paths, target_version, &block)
-        end
-      end
+  class MigrationContext # :nodoc:
+    attr_reader :migrations_paths
 
-      def rollback(migrations_paths, steps = 1)
-        move(:down, migrations_paths, steps)
-      end
+    def initialize(migrations_paths)
+      @migrations_paths = migrations_paths
+    end
 
-      def forward(migrations_paths, steps = 1)
-        move(:up, migrations_paths, steps)
+    def migrate(target_version = nil, &block)
+      case
+      when target_version.nil?
+        up(target_version, &block)
+      when current_version == 0 && target_version == 0
+        []
+      when current_version > target_version
+        down(target_version, &block)
+      else
+        up(target_version, &block)
       end
+    end
 
-      def up(migrations_paths, target_version = nil)
-        migrations = migrations(migrations_paths)
-        migrations.select! { |m| yield m } if block_given?
+    def rollback(steps = 1)
+      move(:down, steps)
+    end
 
-        new(:up, migrations, target_version).migrate
+    def forward(steps = 1)
+      move(:up, steps)
+    end
+
+    def up(target_version = nil)
+      selected_migrations = if block_given?
+        migrations.select { |m| yield m }
+      else
+        migrations
       end
 
-      def down(migrations_paths, target_version = nil)
-        migrations = migrations(migrations_paths)
-        migrations.select! { |m| yield m } if block_given?
+      Migrator.new(:up, selected_migrations, target_version).migrate
+    end
 
-        new(:down, migrations, target_version).migrate
+    def down(target_version = nil)
+      selected_migrations = if block_given?
+        migrations.select { |m| yield m }
+      else
+        migrations
       end
 
-      def run(direction, migrations_paths, target_version)
-        new(direction, migrations(migrations_paths), target_version).run
-      end
+      Migrator.new(:down, selected_migrations, target_version).migrate
+    end
 
-      def open(migrations_paths)
-        new(:up, migrations(migrations_paths), nil)
-      end
+    def run(direction, target_version)
+      Migrator.new(direction, migrations, target_version).run
+    end
 
-      def get_all_versions
-        if SchemaMigration.table_exists?
-          SchemaMigration.all_versions.map(&:to_i)
-        else
-          []
-        end
-      end
+    def open
+      Migrator.new(:up, migrations, nil)
+    end
 
-      def current_version(connection = nil)
-        get_all_versions.max || 0
-      rescue ActiveRecord::NoDatabaseError
+    def get_all_versions
+      if SchemaMigration.table_exists?
+        SchemaMigration.all_versions.map(&:to_i)
+      else
+        []
       end
+    end
 
-      def needs_migration?(connection = nil)
-        (migrations(migrations_paths).collect(&:version) - get_all_versions).size > 0
-      end
+    def current_version
+      get_all_versions.max || 0
+    rescue ActiveRecord::NoDatabaseError
+    end
 
-      def any_migrations?
-        migrations(migrations_paths).any?
-      end
+    def needs_migration?
+      (migrations.collect(&:version) - get_all_versions).size > 0
+    end
 
-      def last_migration #:nodoc:
-        migrations(migrations_paths).last || NullMigration.new
-      end
+    def any_migrations?
+      migrations.any?
+    end
 
-      def migrations_paths
-        @migrations_paths ||= ["db/migrate"]
-        # just to not break things if someone uses: migrations_path = some_string
-        Array(@migrations_paths)
-      end
+    def last_migration #:nodoc:
+      migrations.last || NullMigration.new
+    end
 
-      def parse_migration_filename(filename) # :nodoc:
-        File.basename(filename).scan(Migration::MigrationFilenameRegexp).first
+    def parse_migration_filename(filename) # :nodoc:
+      File.basename(filename).scan(Migration::MigrationFilenameRegexp).first
+    end
+
+    def migrations
+      migrations = migration_files.map do |file|
+        version, name, scope = parse_migration_filename(file)
+        raise IllegalMigrationNameError.new(file) unless version
+        version = version.to_i
+        name = name.camelize
+
+        MigrationProxy.new(name, version, file, scope)
       end
 
-      def migrations(paths)
-        paths = Array(paths)
+      migrations.sort_by(&:version)
+    end
 
-        migrations = migration_files(paths).map do |file|
-          version, name, scope = parse_migration_filename(file)
-          raise IllegalMigrationNameError.new(file) unless version
-          version = version.to_i
-          name = name.camelize
+    def migrations_status
+      db_list = ActiveRecord::SchemaMigration.normalized_versions
 
-          MigrationProxy.new(name, version, file, scope)
-        end
+      file_list = migration_files.map do |file|
+        version, name, scope = parse_migration_filename(file)
+        raise IllegalMigrationNameError.new(file) unless version
+        version = ActiveRecord::SchemaMigration.normalize_migration_number(version)
+        status = db_list.delete(version) ? "up" : "down"
+        [status, version, (name + scope).humanize]
+      end.compact
 
-        migrations.sort_by(&:version)
+      db_list.map! do |version|
+        ["up", version, "********** NO FILE **********"]
       end
 
-      def migrations_status(paths)
-        paths = Array(paths)
-
-        db_list = ActiveRecord::SchemaMigration.normalized_versions
+      (db_list + file_list).sort_by { |_, version, _| version }
+    end
 
-        file_list = migration_files(paths).map do |file|
-          version, name, scope = parse_migration_filename(file)
-          raise IllegalMigrationNameError.new(file) unless version
-          version = ActiveRecord::SchemaMigration.normalize_migration_number(version)
-          status = db_list.delete(version) ? "up" : "down"
-          [status, version, (name + scope).humanize]
-        end.compact
+    def migration_files
+      paths = Array(migrations_paths)
+      Dir[*paths.flat_map { |path| "#{path}/**/[0-9]*_*.rb" }]
+    end
 
-        db_list.map! do |version|
-          ["up", version, "********** NO FILE **********"]
-        end
+    def current_environment
+      ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
+    end
 
-        (db_list + file_list).sort_by { |_, version, _| version }
-      end
+    def protected_environment?
+      ActiveRecord::Base.protected_environments.include?(last_stored_environment) if last_stored_environment
+    end
 
-      def migration_files(paths)
-        Dir[*paths.flat_map { |path| "#{path}/**/[0-9]*_*.rb" }]
-      end
+    def last_stored_environment
+      return nil if current_version == 0
+      raise NoEnvironmentInSchemaError unless ActiveRecord::InternalMetadata.table_exists?
 
-      private
+      environment = ActiveRecord::InternalMetadata[:environment]
+      raise NoEnvironmentInSchemaError unless environment
+      environment
+    end
 
-      def move(direction, migrations_paths, steps)
-        migrator = new(direction, migrations(migrations_paths))
+    private
+      def move(direction, steps)
+        migrator = Migrator.new(direction, migrations)
 
         if current_version != 0 && !migrator.current_migration
           raise UnknownMigrationVersionError.new(current_version)
@@ -1137,10 +1152,29 @@ module ActiveRecord
 
         finish = migrator.migrations[start_index + steps]
         version = finish ? finish.version : 0
-        send(direction, migrations_paths, version)
+        send(direction, version)
+      end
+  end
+
+  class Migrator # :nodoc:
+    class << self
+      attr_accessor :migrations_paths
+
+      def migrations_path=(path)
+        ActiveSupport::Deprecation.warn \
+          "ActiveRecord::Migrator.migrations_paths= is now deprecated and will be removed in Rails 6.0." \
+          "You can set the `migrations_paths` on the `connection` instead through the `database.yml`."
+        self.migrations_paths = [path]
+      end
+
+      # For cases where a table doesn't exist like loading from schema cache
+      def current_version
+        MigrationContext.new(migrations_paths).current_version
       end
     end
 
+    self.migrations_paths = ["db/migrate"]
+
     def initialize(direction, migrations, target_version = nil)
       @direction         = direction
       @target_version    = target_version
@@ -1203,7 +1237,7 @@ module ActiveRecord
     end
 
     def load_migrated
-      @migrated_versions = Set.new(self.class.get_all_versions)
+      @migrated_versions = Set.new(Base.connection.migration_context.get_all_versions)
     end
 
     private
@@ -1235,7 +1269,7 @@ module ActiveRecord
       # Stores the current environment in the database.
       def record_environment
         return if down?
-        ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+        ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Base.connection.migration_context.current_environment
       end
 
       def ran?(migration)
@@ -1294,23 +1328,6 @@ module ActiveRecord
         end
       end
 
-      def self.last_stored_environment
-        return nil if current_version == 0
-        raise NoEnvironmentInSchemaError unless ActiveRecord::InternalMetadata.table_exists?
-
-        environment = ActiveRecord::InternalMetadata[:environment]
-        raise NoEnvironmentInSchemaError unless environment
-        environment
-      end
-
-      def self.current_environment
-        ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
-      end
-
-      def self.protected_environment?
-        ActiveRecord::Base.protected_environments.include?(last_stored_environment) if last_stored_environment
-      end
-
       def up?
         @direction == :up
       end
diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index 81ef4828f8..087632b10f 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -85,7 +85,7 @@ module ActiveRecord
       # invert the +command+.
       def inverse_of(command, args, &block)
         method = :"invert_#{command}"
-        raise IrreversibleMigration, <<-MSG.strip_heredoc unless respond_to?(method, true)
+        raise IrreversibleMigration, <<~MSG unless respond_to?(method, true)
           This migration uses #{command}, which is not automatically reversible.
           To make the migration reversible you can either:
           1. Define #up and #down methods in place of the #change method.
diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 7ae8073478..0edaaa0cf9 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -13,7 +13,10 @@ module ActiveRecord
         const_get(name)
       end
 
-      V5_2 = Current
+      V6_0 = Current
+
+      class V5_2 < V6_0
+      end
 
       class V5_1 < V5_2
         def change_column(table_name, column_name, type, options = {})
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index fa7537c1a3..b04dc04899 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -361,8 +361,9 @@ module ActiveRecord
       # it).
       #
       # +attr_name+ The name of the attribute to retrieve the type for. Must be
-      # a string
+      # a string or a symbol.
       def type_for_attribute(attr_name, &block)
+        attr_name = attr_name.to_s
         if block
           attribute_types.fetch(attr_name, &block)
         else
@@ -378,6 +379,7 @@ module ActiveRecord
       end
 
       def _default_attributes # :nodoc:
+        load_schema
         @default_attributes ||= ActiveModel::AttributeSet.new({})
       end
 
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index c1b1a5334a..88b971327b 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -359,10 +359,10 @@ module ActiveRecord
     # Any change to the attributes on either instance will affect both instances.
     # If you want to change the sti column as well, use #becomes! instead.
     def becomes(klass)
-      became = klass.new
+      became = klass.allocate
+      became.send(:initialize)
       became.instance_variable_set("@attributes", @attributes)
       became.instance_variable_set("@mutations_from_database", @mutations_from_database) if defined?(@mutations_from_database)
-      became.instance_variable_set("@changed_attributes", attributes_changed_by_setter)
       became.instance_variable_set("@new_record", new_record?)
       became.instance_variable_set("@destroyed", destroyed?)
       became.errors.copy!(errors)
@@ -418,6 +418,7 @@ module ActiveRecord
     end
 
     alias update_attributes update
+    deprecate :update_attributes
 
     # Updates its receiver just like #update but calls #save! instead
     # of +save+, so an exception is raised if the record is invalid and saving will fail.
@@ -431,6 +432,7 @@ module ActiveRecord
     end
 
     alias update_attributes! update!
+    deprecate :update_attributes!
 
     # Equivalent to <code>update_columns(name => value)</code>.
     def update_column(name, value)
diff --git a/activerecord/lib/active_record/query_cache.rb b/activerecord/lib/active_record/query_cache.rb
index 8e23128333..c8e340712d 100644
--- a/activerecord/lib/active_record/query_cache.rb
+++ b/activerecord/lib/active_record/query_cache.rb
@@ -7,20 +7,20 @@ module ActiveRecord
       # Enable the query cache within the block if Active Record is configured.
       # If it's not, it will execute the given block.
       def cache(&block)
-        if configurations.empty?
-          yield
-        else
+        if connected? || !configurations.empty?
           connection.cache(&block)
+        else
+          yield
         end
       end
 
       # Disable the query cache within the block if Active Record is configured.
       # If it's not, it will execute the given block.
       def uncached(&block)
-        if configurations.empty?
-          yield
-        else
+        if connected? || !configurations.empty?
           connection.uncached(&block)
+        else
+          yield
         end
       end
     end
diff --git a/activerecord/lib/active_record/querying.rb b/activerecord/lib/active_record/querying.rb
index 3996d5661f..7c8f794910 100644
--- a/activerecord/lib/active_record/querying.rb
+++ b/activerecord/lib/active_record/querying.rb
@@ -5,7 +5,7 @@ module ActiveRecord
     delegate :find, :take, :take!, :first, :first!, :last, :last!, :exists?, :any?, :many?, :none?, :one?, to: :all
     delegate :second, :second!, :third, :third!, :fourth, :fourth!, :fifth, :fifth!, :forty_two, :forty_two!, :third_to_last, :third_to_last!, :second_to_last, :second_to_last!, to: :all
     delegate :first_or_create, :first_or_create!, :first_or_initialize, to: :all
-    delegate :find_or_create_by, :find_or_create_by!, :find_or_initialize_by, to: :all
+    delegate :find_or_create_by, :find_or_create_by!, :create_or_find_by, :create_or_find_by!, :find_or_initialize_by, to: :all
     delegate :find_by, :find_by!, to: :all
     delegate :destroy_all, :delete_all, :update_all, to: :all
     delegate :find_each, :find_in_batches, :in_batches, to: :all
diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 4538ed6a5f..ade5946dd5 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -59,6 +59,7 @@ module ActiveRecord
         console = ActiveSupport::Logger.new(STDERR)
         Rails.logger.extend ActiveSupport::Logger.broadcast console
       end
+      ActiveRecord::Base.verbose_query_logs = false
     end
 
     runner do
@@ -91,6 +92,7 @@ module ActiveRecord
 
             if File.file?(filename)
               current_version = ActiveRecord::Migrator.current_version
+
               next if current_version.nil?
 
               cache = YAML.load(File.read(filename))
diff --git a/activerecord/lib/active_record/railties/controller_runtime.rb b/activerecord/lib/active_record/railties/controller_runtime.rb
index 2ae733f657..309441a057 100644
--- a/activerecord/lib/active_record/railties/controller_runtime.rb
+++ b/activerecord/lib/active_record/railties/controller_runtime.rb
@@ -8,49 +8,44 @@ module ActiveRecord
     module ControllerRuntime #:nodoc:
       extend ActiveSupport::Concern
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
-
-      attr_internal :db_runtime
-
-    private
-
-      def process_action(action, *args)
-        # We also need to reset the runtime before each action
-        # because of queries in middleware or in cases we are streaming
-        # and it won't be cleaned up by the method below.
-        ActiveRecord::LogSubscriber.reset_runtime
-        super
+      module ClassMethods # :nodoc:
+        def log_process_action(payload)
+          messages, db_runtime = super, payload[:db_runtime]
+          messages << ("ActiveRecord: %.1fms" % db_runtime.to_f) if db_runtime
+          messages
+        end
       end
 
-      def cleanup_view_runtime
-        if logger && logger.info? && ActiveRecord::Base.connected?
-          db_rt_before_render = ActiveRecord::LogSubscriber.reset_runtime
-          self.db_runtime = (db_runtime || 0) + db_rt_before_render
-          runtime = super
-          db_rt_after_render = ActiveRecord::LogSubscriber.reset_runtime
-          self.db_runtime += db_rt_after_render
-          runtime - db_rt_after_render
-        else
+      private
+        attr_internal :db_runtime
+
+        def process_action(action, *args)
+          # We also need to reset the runtime before each action
+          # because of queries in middleware or in cases we are streaming
+          # and it won't be cleaned up by the method below.
+          ActiveRecord::LogSubscriber.reset_runtime
           super
         end
-      end
 
-      def append_info_to_payload(payload)
-        super
-        if ActiveRecord::Base.connected?
-          payload[:db_runtime] = (db_runtime || 0) + ActiveRecord::LogSubscriber.reset_runtime
+        def cleanup_view_runtime
+          if logger && logger.info? && ActiveRecord::Base.connected?
+            db_rt_before_render = ActiveRecord::LogSubscriber.reset_runtime
+            self.db_runtime = (db_runtime || 0) + db_rt_before_render
+            runtime = super
+            db_rt_after_render = ActiveRecord::LogSubscriber.reset_runtime
+            self.db_runtime += db_rt_after_render
+            runtime - db_rt_after_render
+          else
+            super
+          end
         end
-      end
 
-      module ClassMethods # :nodoc:
-        def log_process_action(payload)
-          messages, db_runtime = super, payload[:db_runtime]
-          messages << ("ActiveRecord: %.1fms" % db_runtime.to_f) if db_runtime
-          messages
+        def append_info_to_payload(payload)
+          super
+          if ActiveRecord::Base.connected?
+            payload[:db_runtime] = (db_runtime || 0) + ActiveRecord::LogSubscriber.reset_runtime
+          end
         end
-      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/railties/databases.rake b/activerecord/lib/active_record/railties/databases.rake
index fce3e1c5cf..662a8bc720 100644
--- a/activerecord/lib/active_record/railties/databases.rake
+++ b/activerecord/lib/active_record/railties/databases.rake
@@ -6,7 +6,7 @@ db_namespace = namespace :db do
   desc "Set the environment value for the database"
   task "environment:set" => :load_config do
     ActiveRecord::InternalMetadata.create_table
-    ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+    ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Base.connection.migration_context.current_environment
   end
 
   task check_protected_environments: :load_config do
@@ -99,9 +99,8 @@ db_namespace = namespace :db do
 
       ActiveRecord::Tasks::DatabaseTasks.check_target_version
 
-      ActiveRecord::Migrator.run(
+      ActiveRecord::Base.connection.migration_context.run(
         :up,
-        ActiveRecord::Tasks::DatabaseTasks.migrations_paths,
         ActiveRecord::Tasks::DatabaseTasks.target_version
       )
       db_namespace["_dump"].invoke
@@ -113,9 +112,8 @@ db_namespace = namespace :db do
 
       ActiveRecord::Tasks::DatabaseTasks.check_target_version
 
-      ActiveRecord::Migrator.run(
+      ActiveRecord::Base.connection.migration_context.run(
         :down,
-        ActiveRecord::Tasks::DatabaseTasks.migrations_paths,
         ActiveRecord::Tasks::DatabaseTasks.target_version
       )
       db_namespace["_dump"].invoke
@@ -131,8 +129,7 @@ db_namespace = namespace :db do
       puts "\ndatabase: #{ActiveRecord::Base.connection_config[:database]}\n\n"
       puts "#{'Status'.center(8)}  #{'Migration ID'.ljust(14)}  Migration Name"
       puts "-" * 50
-      paths = ActiveRecord::Tasks::DatabaseTasks.migrations_paths
-      ActiveRecord::Migrator.migrations_status(paths).each do |status, version, name|
+      ActiveRecord::Base.connection.migration_context.migrations_status.each do |status, version, name|
         puts "#{status.center(8)}  #{version.ljust(14)}  #{name}"
       end
       puts
@@ -142,14 +139,14 @@ db_namespace = namespace :db do
   desc "Rolls the schema back to the previous version (specify steps w/ STEP=n)."
   task rollback: :load_config do
     step = ENV["STEP"] ? ENV["STEP"].to_i : 1
-    ActiveRecord::Migrator.rollback(ActiveRecord::Tasks::DatabaseTasks.migrations_paths, step)
+    ActiveRecord::Base.connection.migration_context.rollback(step)
     db_namespace["_dump"].invoke
   end
 
   # desc 'Pushes the schema to the next version (specify steps w/ STEP=n).'
   task forward: :load_config do
     step = ENV["STEP"] ? ENV["STEP"].to_i : 1
-    ActiveRecord::Migrator.forward(ActiveRecord::Tasks::DatabaseTasks.migrations_paths, step)
+    ActiveRecord::Base.connection.migration_context.forward(step)
     db_namespace["_dump"].invoke
   end
 
@@ -172,12 +169,12 @@ db_namespace = namespace :db do
 
   desc "Retrieves the current schema version number"
   task version: :load_config do
-    puts "Current version: #{ActiveRecord::Migrator.current_version}"
+    puts "Current version: #{ActiveRecord::Base.connection.migration_context.current_version}"
   end
 
   # desc "Raises an error if there are pending migrations"
   task abort_if_pending_migrations: :load_config do
-    pending_migrations = ActiveRecord::Migrator.open(ActiveRecord::Tasks::DatabaseTasks.migrations_paths).pending_migrations
+    pending_migrations = ActiveRecord::Base.connection.migration_context.open.pending_migrations
 
     if pending_migrations.any?
       puts "You have #{pending_migrations.size} pending #{pending_migrations.size > 1 ? 'migrations:' : 'migration:'}"
@@ -232,7 +229,7 @@ db_namespace = namespace :db do
       base_dir = ActiveRecord::Tasks::DatabaseTasks.fixtures_path
 
       Dir["#{base_dir}/**/*.yml"].each do |file|
-        if data = YAML::load(ERB.new(IO.read(file)).result)
+        if data = YAML.load(ERB.new(IO.read(file)).result)
           data.each_key do |key|
             key_id = ActiveRecord::FixtureSet.identify(key)
 
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index c28e31a3da..c66c7778f4 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -291,7 +291,11 @@ module ActiveRecord
       end
 
       def build_scope(table, predicate_builder = predicate_builder(table))
-        Relation.create(klass, table, predicate_builder)
+        Relation.create(
+          klass,
+          table: table,
+          predicate_builder: predicate_builder
+        )
       end
 
       def join_primary_key(*)
@@ -958,16 +962,14 @@ module ActiveRecord
         collect_join_reflections(seed + [self])
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
-        attr_reader :delegate_reflection
-
         def actual_source_reflection # FIXME: this is a horrible name
           source_reflection.actual_source_reflection
         end
 
       private
+        attr_reader :delegate_reflection
+
         def collect_join_reflections(seed)
           a = source_reflection.add_as_source seed
           if options[:source_type]
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 10be583ef4..736173ae1b 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -22,7 +22,7 @@ module ActiveRecord
     alias :loaded? :loaded
     alias :locked? :lock_value
 
-    def initialize(klass, table, predicate_builder, values = {})
+    def initialize(klass, table: klass.arel_table, predicate_builder: klass.predicate_builder, values: {})
       @klass  = klass
       @table  = table
       @values = values
@@ -142,23 +142,12 @@ module ActiveRecord
     # failed due to validation errors it won't be persisted, you get what
     # #create returns in such situation.
     #
-    # Please note *this method is not atomic*, it runs first a SELECT, and if
+    # Please note <b>this method is not atomic</b>, it runs first a SELECT, and if
     # there are no results an INSERT is attempted. If there are other threads
     # or processes there is a race condition between both calls and it could
     # be the case that you end up with two similar records.
     #
-    # Whether that is a problem or not depends on the logic of the
-    # application, but in the particular case in which rows have a UNIQUE
-    # constraint an exception may be raised, just retry:
-    #
-    #  begin
-    #    CreditAccount.transaction(requires_new: true) do
-    #      CreditAccount.find_or_create_by(user_id: user.id)
-    #    end
-    #  rescue ActiveRecord::RecordNotUnique
-    #    retry
-    #  end
-    #
+    # If this might be a problem for your application, please see #create_or_find_by.
     def find_or_create_by(attributes, &block)
       find_by(attributes) || create(attributes, &block)
     end
@@ -170,6 +159,47 @@ module ActiveRecord
       find_by(attributes) || create!(attributes, &block)
     end
 
+    # Attempts to create a record with the given attributes in a table that has a unique constraint
+    # on one or several of its columns. If a row already exists with one or several of these
+    # unique constraints, the exception such an insertion would normally raise is caught,
+    # and the existing record with those attributes is found using #find_by.
+    #
+    # This is similar to #find_or_create_by, but avoids the problem of stale reads between the SELECT
+    # and the INSERT, as that method needs to first query the table, then attempt to insert a row
+    # if none is found.
+    #
+    # There are several drawbacks to #create_or_find_by, though:
+    #
+    # * The underlying table must have the relevant columns defined with unique constraints.
+    # * A unique constraint violation may be triggered by only one, or at least less than all,
+    #   of the given attributes. This means that the subsequent #find_by may fail to find a
+    #   matching record, which will then raise an <tt>ActiveRecord::RecordNotFound</tt> exception,
+    #   rather than a record with the given attributes.
+    # * While we avoid the race condition between SELECT -> INSERT from #find_or_create_by,
+    #   we actually have another race condition between INSERT -> SELECT, which can be triggered
+    #   if a DELETE between those two statements is run by another client. But for most applications,
+    #   that's a significantly less likely condition to hit.
+    # * It relies on exception handling to handle control flow, which may be marginally slower.
+    #
+    # This method will return a record if all given attributes are covered by unique constraints
+    # (unless the INSERT -> DELETE -> SELECT race condition is triggered), but if creation was attempted
+    # and failed due to validation errors it won't be persisted, you get what #create returns in
+    # such situation.
+    def create_or_find_by(attributes, &block)
+      transaction(requires_new: true) { create(attributes, &block) }
+    rescue ActiveRecord::RecordNotUnique
+      find_by!(attributes)
+    end
+
+    # Like #create_or_find_by, but calls
+    # {create!}[rdoc-ref:Persistence::ClassMethods#create!] so an exception
+    # is raised if the created record is invalid.
+    def create_or_find_by!(attributes, &block)
+      transaction(requires_new: true) { create!(attributes, &block) }
+    rescue ActiveRecord::RecordNotUnique
+      find_by!(attributes)
+    end
+
     # Like #find_or_create_by, but calls {new}[rdoc-ref:Core#new]
     # instead of {create}[rdoc-ref:Persistence::ClassMethods#create].
     def find_or_initialize_by(attributes, &block)
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index cb0b06cfdc..6a63eb70b1 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -131,7 +131,14 @@ module ActiveRecord
     def calculate(operation, column_name)
       if has_include?(column_name)
         relation = apply_join_dependency
-        relation.distinct! if operation.to_s.downcase == "count"
+
+        if operation.to_s.downcase == "count" && !distinct_value
+          relation.distinct!
+          # PostgreSQL: ORDER BY expressions must appear in SELECT list when using DISTINCT
+          if (column_name == :all || column_name.nil?) && select_values.empty?
+            relation.order_values = []
+          end
+        end
 
         relation.calculate(operation, column_name)
       else
@@ -193,6 +200,24 @@ module ActiveRecord
       end
     end
 
+    # Pick the value(s) from the named column(s) in the current relation.
+    # This is short-hand for <tt>relation.limit(1).pluck(*column_names).first</tt>, and is primarily useful
+    # when you have a relation that's already narrowed down to a single row.
+    #
+    # Just like #pluck, #pick will only load the actual value, not the entire record object, so it's also
+    # more efficient. The value is, again like with pluck, typecast by the column type.
+    #
+    #   Person.where(id: 1).pick(:name)
+    #   # SELECT people.name FROM people WHERE id = 1 LIMIT 1
+    #   # => 'David'
+    #
+    #   Person.where(id: 1).pick(:name, :email_address)
+    #   # SELECT people.name, people.email_address FROM people WHERE id = 1 LIMIT 1
+    #   # => [ 'David', 'david@loudthinking.com' ]
+    def pick(*column_names)
+      limit(1).pluck(*column_names).first
+    end
+
     # Pluck all the ID's for the relation using the table's primary key
     #
     #   Person.ids # SELECT people.id FROM people
@@ -235,7 +260,7 @@ module ActiveRecord
       def aggregate_column(column_name)
         return column_name if Arel::Expressions === column_name
 
-        if @klass.has_attribute?(column_name.to_s) || @klass.attribute_alias?(column_name.to_s)
+        if @klass.has_attribute?(column_name) || @klass.attribute_alias?(column_name)
           @klass.arel_attribute(column_name)
         else
           Arel.sql(column_name == :all ? "*" : column_name.to_s)
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 4863befec8..4b16b49cdf 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -38,7 +38,7 @@ module ActiveRecord
     # may vary depending on the klass of a relation, so we create a subclass of Relation
     # for each different klass, and the delegations are compiled into that subclass only.
 
-    delegate :to_xml, :encode_with, :length, :each, :uniq, :join,
+    delegate :to_xml, :encode_with, :length, :each, :join,
              :[], :&, :|, :+, :-, :sample, :reverse, :rotate, :compact, :in_groups, :in_groups_of,
              :to_sentence, :to_formatted_s, :as_json,
              :shuffle, :split, :slice, :index, :rindex, to: :records
diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index ebdd4144bb..25510d4a57 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -23,7 +23,11 @@ module ActiveRecord
       # build a relation to merge in rather than directly merging
       # the values.
       def other
-        other = Relation.create(relation.klass, relation.table, relation.predicate_builder)
+        other = Relation.create(
+          relation.klass,
+          table: relation.table,
+          predicate_builder: relation.predicate_builder
+        )
         hash.each { |k, v|
           if k == :joins
             if Hash === v
diff --git a/activerecord/lib/active_record/relation/predicate_builder.rb b/activerecord/lib/active_record/relation/predicate_builder.rb
index 885c26d7aa..7a0edcbc33 100644
--- a/activerecord/lib/active_record/relation/predicate_builder.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder.rb
@@ -57,9 +57,6 @@ module ActiveRecord
     end
 
     protected
-
-      attr_reader :table
-
       def expand_from_hash(attributes)
         return ["1=0"] if attributes.empty?
 
@@ -86,6 +83,18 @@ module ActiveRecord
               expand_from_hash(query).reduce(&:and)
             end
             queries.reduce(&:or)
+          elsif table.aggregated_with?(key)
+            mapping = table.reflect_on_aggregation(key).mapping
+            queries = Array.wrap(value).map do |object|
+              mapping.map do |field_attr, aggregate_attr|
+                if mapping.size == 1 && !object.respond_to?(aggregate_attr)
+                  build(table.arel_attribute(field_attr), object)
+                else
+                  build(table.arel_attribute(field_attr), object.send(aggregate_attr))
+                end
+              end.reduce(&:and)
+            end
+            queries.reduce(&:or)
           # FIXME: Deprecate this and provide a public API to force equality
           elsif (value.is_a?(Range) || value.is_a?(Array)) &&
             table.type(key.to_s).respond_to?(:subtype)
@@ -97,6 +106,7 @@ module ActiveRecord
       end
 
     private
+      attr_reader :table
 
       def associated_predicate_builder(association_name)
         self.class.new(table.associated_table(association_name))
diff --git a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
index 2fd75c8958..64bf83e3c1 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
@@ -34,8 +34,7 @@ module ActiveRecord
         array_predicates.inject(&:or)
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
 
         module NullPredicate # :nodoc:
diff --git a/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb b/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
index 28c7483c95..88cd71cf69 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/association_query_value.rb
@@ -12,12 +12,9 @@ module ActiveRecord
         [associated_table.association_join_foreign_key.to_s => ids]
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :associated_table, :value
 
-      private
         def ids
           case value
           when Relation
diff --git a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
index 112821135f..10c5c1a66a 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/base_handler.rb
@@ -11,8 +11,7 @@ module ActiveRecord
         predicate_builder.build(attribute, value.id)
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
index 34db266f05..e8c9f60860 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/basic_object_handler.rb
@@ -12,8 +12,7 @@ module ActiveRecord
         attribute.eq(bind)
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
index e8e2f2c626..a5e9a0473e 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/polymorphic_array_value.rb
@@ -17,12 +17,9 @@ module ActiveRecord
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
+      private
         attr_reader :associated_table, :values
 
-      private
         def type_to_ids_mapping
           default_hash = Hash.new { |hsh, key| hsh[key] = [] }
           values.each_with_object(default_hash) { |value, hash| hash[base_class(value).name] << convert_to_id(value) }
diff --git a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
index 6d16579708..44bb2c7ab6 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/range_handler.rb
@@ -16,15 +16,16 @@ module ActiveRecord
       def call(attribute, value)
         begin_bind = predicate_builder.build_bind_attribute(attribute.name, value.begin)
         end_bind = predicate_builder.build_bind_attribute(attribute.name, value.end)
-        if value.begin.respond_to?(:infinite?) && value.begin.infinite?
-          if value.end.respond_to?(:infinite?) && value.end.infinite?
+
+        if begin_bind.value.infinity?
+          if end_bind.value.infinity?
             attribute.not_in([])
           elsif value.exclude_end?
             attribute.lt(end_bind)
           else
             attribute.lteq(end_bind)
           end
-        elsif value.end.respond_to?(:infinite?) && value.end.infinite?
+        elsif end_bind.value.infinity?
           attribute.gteq(begin_bind)
         elsif value.exclude_end?
           attribute.gteq(begin_bind).and(attribute.lt(end_bind))
@@ -33,8 +34,7 @@ module ActiveRecord
         end
       end
 
-      protected
-
+      private
         attr_reader :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/relation/query_attribute.rb b/activerecord/lib/active_record/relation/query_attribute.rb
index 3532f28858..f64bd30d38 100644
--- a/activerecord/lib/active_record/relation/query_attribute.rb
+++ b/activerecord/lib/active_record/relation/query_attribute.rb
@@ -21,6 +21,23 @@ module ActiveRecord
         !value_before_type_cast.is_a?(StatementCache::Substitute) &&
           (value_before_type_cast.nil? || value_for_database.nil?)
       end
+
+      def boundable?
+        return @_boundable if defined?(@_boundable)
+        nil?
+        @_boundable = true
+      rescue ::RangeError
+        @_boundable = false
+      end
+
+      def infinity?
+        _infinity?(value_before_type_cast) || boundable? && _infinity?(value_for_database)
+      end
+
+      private
+        def _infinity?(value)
+          value.respond_to?(:infinite?) && value.infinite?
+        end
     end
   end
 end
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 86882c7ce7..3afa368575 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -231,6 +231,7 @@ module ActiveRecord
     end
 
     def _select!(*fields) # :nodoc:
+      fields.reject!(&:blank?)
       fields.flatten!
       fields.map! do |field|
         klass.attribute_alias?(field) ? klass.attribute_alias(field).to_sym : field
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index 617d8de8b2..562e04194c 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -69,7 +69,7 @@ module ActiveRecord
     private
 
       def relation_with(values)
-        result = Relation.create(klass, table, predicate_builder, values)
+        result = Relation.create(klass, values: values)
         result.extend(*extending_values) if extending_values.any?
         result
       end
diff --git a/activerecord/lib/active_record/relation/where_clause_factory.rb b/activerecord/lib/active_record/relation/where_clause_factory.rb
index 4ae94f4bfe..c1b3eea9df 100644
--- a/activerecord/lib/active_record/relation/where_clause_factory.rb
+++ b/activerecord/lib/active_record/relation/where_clause_factory.rb
@@ -14,7 +14,6 @@ module ActiveRecord
           parts = [klass.sanitize_sql(other.empty? ? opts : ([opts] + other))]
         when Hash
           attributes = predicate_builder.resolve_column_aliases(opts)
-          attributes = klass.send(:expand_hash_conditions_for_aggregates, attributes)
           attributes.stringify_keys!
 
           parts = predicate_builder.build_from_hash(attributes)
@@ -27,8 +26,7 @@ module ActiveRecord
         WhereClause.new(parts)
       end
 
-      protected
-
+      private
         attr_reader :klass, :predicate_builder
     end
   end
diff --git a/activerecord/lib/active_record/sanitization.rb b/activerecord/lib/active_record/sanitization.rb
index 58da106092..c6c268855e 100644
--- a/activerecord/lib/active_record/sanitization.rb
+++ b/activerecord/lib/active_record/sanitization.rb
@@ -84,7 +84,7 @@ module ActiveRecord
       def sanitize_sql_hash_for_assignment(attrs, table)
         c = connection
         attrs.map do |attr, value|
-          type = type_for_attribute(attr.to_s)
+          type = type_for_attribute(attr)
           value = type.serialize(type.cast(value))
           "#{c.quote_table_name_for_assignment(table, attr)} = #{c.quote(value)}"
         end.join(", ")
@@ -155,10 +155,12 @@ module ActiveRecord
             if aggregation = reflect_on_aggregation(attr.to_sym)
               mapping = aggregation.mapping
               mapping.each do |field_attr, aggregate_attr|
-                if mapping.size == 1 && !value.respond_to?(aggregate_attr)
-                  expanded_attrs[field_attr] = value
+                expanded_attrs[field_attr] = if value.is_a?(Array)
+                  value.map { |it| it.send(aggregate_attr) }
+                elsif mapping.size == 1 && !value.respond_to?(aggregate_attr)
+                  value
                 else
-                  expanded_attrs[field_attr] = value.send(aggregate_attr)
+                  value.send(aggregate_attr)
                 end
               end
             else
@@ -167,6 +169,7 @@ module ActiveRecord
           end
           expanded_attrs
         end
+        deprecate :expand_hash_conditions_for_aggregates
 
         def replace_bind_variables(statement, values)
           raise_if_bind_arity_mismatch(statement, statement.count("?"), values.size)
diff --git a/activerecord/lib/active_record/schema.rb b/activerecord/lib/active_record/schema.rb
index 1e121f2a09..216359867c 100644
--- a/activerecord/lib/active_record/schema.rb
+++ b/activerecord/lib/active_record/schema.rb
@@ -55,7 +55,7 @@ module ActiveRecord
       end
 
       ActiveRecord::InternalMetadata.create_table
-      ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+      ActiveRecord::InternalMetadata[:environment] = connection.migration_context.current_environment
     end
 
     private
diff --git a/activerecord/lib/active_record/schema_dumper.rb b/activerecord/lib/active_record/schema_dumper.rb
index 16ccba6b6c..b8d848b999 100644
--- a/activerecord/lib/active_record/schema_dumper.rb
+++ b/activerecord/lib/active_record/schema_dumper.rb
@@ -44,7 +44,7 @@ module ActiveRecord
 
       def initialize(connection, options = {})
         @connection = connection
-        @version = Migrator::current_version rescue nil
+        @version = connection.migration_context.current_version rescue nil
         @options = options
       end
 
diff --git a/activerecord/lib/active_record/statement_cache.rb b/activerecord/lib/active_record/statement_cache.rb
index 59acd63a0f..b41d3504fd 100644
--- a/activerecord/lib/active_record/statement_cache.rb
+++ b/activerecord/lib/active_record/statement_cache.rb
@@ -114,8 +114,7 @@ module ActiveRecord
       end
     end
 
-    protected
-
+    private
       attr_reader :query_builder, :bind_map, :klass
   end
 end
diff --git a/activerecord/lib/active_record/store.rb b/activerecord/lib/active_record/store.rb
index 202b82fa61..6dbc977f9a 100644
--- a/activerecord/lib/active_record/store.rb
+++ b/activerecord/lib/active_record/store.rb
@@ -135,7 +135,7 @@ module ActiveRecord
       end
 
       def store_accessor_for(store_attribute)
-        type_for_attribute(store_attribute.to_s).accessor
+        type_for_attribute(store_attribute).accessor
       end
 
       class HashAccessor # :nodoc:
diff --git a/activerecord/lib/active_record/table_metadata.rb b/activerecord/lib/active_record/table_metadata.rb
index 0459cbdc59..b67479fb6a 100644
--- a/activerecord/lib/active_record/table_metadata.rb
+++ b/activerecord/lib/active_record/table_metadata.rb
@@ -30,7 +30,7 @@ module ActiveRecord
 
     def type(column_name)
       if klass
-        klass.type_for_attribute(column_name.to_s)
+        klass.type_for_attribute(column_name)
       else
         Type.default_value
       end
@@ -65,10 +65,15 @@ module ActiveRecord
       association && association.polymorphic?
     end
 
-    # TODO Change this to private once we've dropped Ruby 2.2 support.
-    # Workaround for Ruby 2.2 "private attribute?" warning.
-    protected
+    def aggregated_with?(aggregation_name)
+      klass && reflect_on_aggregation(aggregation_name)
+    end
+
+    def reflect_on_aggregation(aggregation_name)
+      klass.reflect_on_aggregation(aggregation_name)
+    end
 
+    private
       attr_reader :klass, :arel_table, :association
   end
 end
diff --git a/activerecord/lib/active_record/tasks/database_tasks.rb b/activerecord/lib/active_record/tasks/database_tasks.rb
index 4657e51e6d..d8e0cd1e30 100644
--- a/activerecord/lib/active_record/tasks/database_tasks.rb
+++ b/activerecord/lib/active_record/tasks/database_tasks.rb
@@ -54,10 +54,10 @@ module ActiveRecord
 
       def check_protected_environments!
         unless ENV["DISABLE_DATABASE_ENVIRONMENT_CHECK"]
-          current = ActiveRecord::Migrator.current_environment
-          stored  = ActiveRecord::Migrator.last_stored_environment
+          current = ActiveRecord::Base.connection.migration_context.current_environment
+          stored  = ActiveRecord::Base.connection.migration_context.last_stored_environment
 
-          if ActiveRecord::Migrator.protected_environment?
+          if ActiveRecord::Base.connection.migration_context.protected_environment?
             raise ActiveRecord::ProtectedEnvironmentError.new(stored)
           end
 
@@ -117,9 +117,9 @@ module ActiveRecord
       def create(*arguments)
         configuration = arguments.first
         class_for_adapter(configuration["adapter"]).new(*arguments).create
-        $stdout.puts "Created database '#{configuration['database']}'"
+        $stdout.puts "Created database '#{configuration['database']}'" if verbose?
       rescue DatabaseAlreadyExists
-        $stderr.puts "Database '#{configuration['database']}' already exists"
+        $stderr.puts "Database '#{configuration['database']}' already exists" if verbose?
       rescue Exception => error
         $stderr.puts error
         $stderr.puts "Couldn't create database for #{configuration.inspect}"
@@ -144,7 +144,7 @@ module ActiveRecord
       def drop(*arguments)
         configuration = arguments.first
         class_for_adapter(configuration["adapter"]).new(*arguments).drop
-        $stdout.puts "Dropped database '#{configuration['database']}'"
+        $stdout.puts "Dropped database '#{configuration['database']}'" if verbose?
       rescue ActiveRecord::NoDatabaseError
         $stderr.puts "Database '#{configuration['database']}' does not exist"
       rescue Exception => error
@@ -163,13 +163,17 @@ module ActiveRecord
         }
       end
 
+      def verbose?
+        ENV["VERBOSE"] ? ENV["VERBOSE"] != "false" : true
+      end
+
       def migrate
         check_target_version
 
-        verbose = ENV["VERBOSE"] ? ENV["VERBOSE"] != "false" : true
+        verbose = verbose?
         scope = ENV["SCOPE"]
         verbose_was, Migration.verbose = Migration.verbose, verbose
-        Migrator.migrate(migrations_paths, target_version) do |migration|
+        Base.connection.migration_context.migrate(target_version) do |migration|
           scope.blank? || scope == migration.scope
         end
         ActiveRecord::Base.clear_cache!
diff --git a/activerecord/lib/active_record/test_databases.rb b/activerecord/lib/active_record/test_databases.rb
new file mode 100644
index 0000000000..606a3b0fb5
--- /dev/null
+++ b/activerecord/lib/active_record/test_databases.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require "active_support/testing/parallelization"
+
+module ActiveRecord
+  module TestDatabases # :nodoc:
+    ActiveSupport::Testing::Parallelization.after_fork_hook do |i|
+      create_and_migrate(i, spec_name: Rails.env)
+    end
+
+    ActiveSupport::Testing::Parallelization.run_cleanup_hook do |i|
+      drop(i, spec_name: Rails.env)
+    end
+
+    def self.create_and_migrate(i, spec_name:)
+      old, ENV["VERBOSE"] = ENV["VERBOSE"], "false"
+
+      connection_spec = ActiveRecord::Base.configurations[spec_name]
+
+      connection_spec["database"] += "-#{i}"
+      ActiveRecord::Tasks::DatabaseTasks.create(connection_spec)
+      ActiveRecord::Base.establish_connection(connection_spec)
+      ActiveRecord::Tasks::DatabaseTasks.migrate
+    ensure
+      ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[Rails.env])
+      ENV["VERBOSE"] = old
+    end
+
+    def self.drop(i, spec_name:)
+      old, ENV["VERBOSE"] = ENV["VERBOSE"], "false"
+      connection_spec = ActiveRecord::Base.configurations[spec_name]
+
+      ActiveRecord::Tasks::DatabaseTasks.drop(connection_spec)
+    ensure
+      ENV["VERBOSE"] = old
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/type/adapter_specific_registry.rb b/activerecord/lib/active_record/type/adapter_specific_registry.rb
index e7468aa542..b300fdfa05 100644
--- a/activerecord/lib/active_record/type/adapter_specific_registry.rb
+++ b/activerecord/lib/active_record/type/adapter_specific_registry.rb
@@ -52,8 +52,6 @@ module ActiveRecord
         priority <=> other.priority
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
       protected
 
         attr_reader :name, :block, :adapter, :override
@@ -114,13 +112,8 @@ module ActiveRecord
         super | 4
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :options, :klass
-
       private
+        attr_reader :options, :klass
 
         def matches_options?(**kwargs)
           options.all? do |key, value|
diff --git a/activerecord/lib/active_record/type_caster/connection.rb b/activerecord/lib/active_record/type_caster/connection.rb
index af4e4e37e2..7cf8181d8e 100644
--- a/activerecord/lib/active_record/type_caster/connection.rb
+++ b/activerecord/lib/active_record/type_caster/connection.rb
@@ -14,15 +14,10 @@ module ActiveRecord
         connection.type_cast_from_column(column, value)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :table_name
         delegate :connection, to: :@klass
 
-      private
-
         def column_for(attribute_name)
           if connection.schema_cache.data_source_exists?(table_name)
             connection.schema_cache.columns_hash(table_name)[attribute_name.to_s]
diff --git a/activerecord/lib/active_record/type_caster/map.rb b/activerecord/lib/active_record/type_caster/map.rb
index d51350ba83..663cdadb03 100644
--- a/activerecord/lib/active_record/type_caster/map.rb
+++ b/activerecord/lib/active_record/type_caster/map.rb
@@ -9,14 +9,11 @@ module ActiveRecord
 
       def type_cast_for_database(attr_name, value)
         return value if value.is_a?(Arel::Nodes::BindParam)
-        type = types.type_for_attribute(attr_name.to_s)
+        type = types.type_for_attribute(attr_name)
         type.serialize(value)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
+      private
         attr_reader :types
     end
   end
diff --git a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
index 856fcc5897..a07b00ef79 100644
--- a/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
+++ b/activerecord/lib/rails/generators/active_record/migration/migration_generator.rb
@@ -15,12 +15,8 @@ module ActiveRecord
         migration_template @migration_template, File.join(db_migrate_path, "#{file_name}.rb")
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :migration_action, :join_tables
-
       private
+        attr_reader :migration_action, :join_tables
 
         # Sets the default migration template that is being used for the generation of the migration.
         # Depending on command line arguments, the migration template and the table name instance
diff --git a/activerecord/test/.gitignore b/activerecord/test/.gitignore
deleted file mode 100644
index a0ec5967dd..0000000000
--- a/activerecord/test/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-/config.yml
diff --git a/activerecord/test/cases/adapter_test.rb b/activerecord/test/cases/adapter_test.rb
index 9aaa2852d0..4c41a68407 100644
--- a/activerecord/test/cases/adapter_test.rb
+++ b/activerecord/test/cases/adapter_test.rb
@@ -20,7 +20,7 @@ module ActiveRecord
         b = Book.create(name: "my \x00 book")
         b.reload
         assert_equal "my \x00 book", b.name
-        b.update_attributes(name: "my other \x00 book")
+        b.update(name: "my other \x00 book")
         b.reload
         assert_equal "my other \x00 book", b.name
       end
@@ -78,7 +78,7 @@ module ActiveRecord
       idx_name = "accounts_idx"
 
       indexes = @connection.indexes("accounts")
-      assert indexes.empty?
+      assert_empty indexes
 
       @connection.add_index :accounts, :firm_id, name: idx_name
       indexes = @connection.indexes("accounts")
@@ -368,16 +368,16 @@ module ActiveRecord
     unless in_memory_db?
       test "transaction state is reset after a reconnect" do
         @connection.begin_transaction
-        assert @connection.transaction_open?
+        assert_predicate @connection, :transaction_open?
         @connection.reconnect!
-        assert !@connection.transaction_open?
+        assert_not_predicate @connection, :transaction_open?
       end
 
       test "transaction state is reset after a disconnect" do
         @connection.begin_transaction
-        assert @connection.transaction_open?
+        assert_predicate @connection, :transaction_open?
         @connection.disconnect!
-        assert !@connection.transaction_open?
+        assert_not_predicate @connection, :transaction_open?
       end
     end
 
diff --git a/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb b/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
index fd5f712f1a..aa870349be 100644
--- a/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/case_sensitivity_test.rb
@@ -14,8 +14,8 @@ class Mysql2CaseSensitivityTest < ActiveRecord::Mysql2TestCase
   end
 
   def test_case_sensitive
-    assert !CollationTest.columns_hash["string_ci_column"].case_sensitive?
-    assert CollationTest.columns_hash["string_cs_column"].case_sensitive?
+    assert_not_predicate CollationTest.columns_hash["string_ci_column"], :case_sensitive?
+    assert_predicate CollationTest.columns_hash["string_cs_column"], :case_sensitive?
   end
 
   def test_case_insensitive_comparison_for_ci_column
diff --git a/activerecord/test/cases/adapters/mysql2/connection_test.rb b/activerecord/test/cases/adapters/mysql2/connection_test.rb
index 13b4096671..726f58d58e 100644
--- a/activerecord/test/cases/adapters/mysql2/connection_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/connection_test.rb
@@ -40,29 +40,29 @@ class Mysql2ConnectionTest < ActiveRecord::Mysql2TestCase
   end
 
   def test_no_automatic_reconnection_after_timeout
-    assert @connection.active?
+    assert_predicate @connection, :active?
     @connection.update("set @@wait_timeout=1")
     sleep 2
-    assert !@connection.active?
+    assert_not_predicate @connection, :active?
   ensure
     # Repair all fixture connections so other tests won't break.
     @fixture_connections.each(&:verify!)
   end
 
   def test_successful_reconnection_after_timeout_with_manual_reconnect
-    assert @connection.active?
+    assert_predicate @connection, :active?
     @connection.update("set @@wait_timeout=1")
     sleep 2
     @connection.reconnect!
-    assert @connection.active?
+    assert_predicate @connection, :active?
   end
 
   def test_successful_reconnection_after_timeout_with_verify
-    assert @connection.active?
+    assert_predicate @connection, :active?
     @connection.update("set @@wait_timeout=1")
     sleep 2
     @connection.verify!
-    assert @connection.active?
+    assert_predicate @connection, :active?
   end
 
   def test_execute_after_disconnect
diff --git a/activerecord/test/cases/adapters/mysql2/enum_test.rb b/activerecord/test/cases/adapters/mysql2/enum_test.rb
index 108bec832c..832f5d61d1 100644
--- a/activerecord/test/cases/adapters/mysql2/enum_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/enum_test.rb
@@ -13,11 +13,11 @@ class Mysql2EnumTest < ActiveRecord::Mysql2TestCase
 
   def test_should_not_be_unsigned
     column = EnumTest.columns_hash["enum_column"]
-    assert_not column.unsigned?
+    assert_not_predicate column, :unsigned?
   end
 
   def test_should_not_be_bigint
     column = EnumTest.columns_hash["enum_column"]
-    assert_not column.bigint?
+    assert_not_predicate column, :bigint?
   end
 end
diff --git a/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb b/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
index 62abd694bb..d7d9a2d732 100644
--- a/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/schema_migrations_test.rb
@@ -36,7 +36,7 @@ class SchemaMigrationsTest < ActiveRecord::Mysql2TestCase
       assert connection.column_exists?(table_name, :key, :string)
     end
   ensure
-    ActiveRecord::InternalMetadata[:environment] = ActiveRecord::Migrator.current_environment
+    ActiveRecord::InternalMetadata[:environment] = connection.migration_context.current_environment
   end
 
   private
diff --git a/activerecord/test/cases/adapters/mysql2/transaction_test.rb b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
index f921515c10..30455fbde5 100644
--- a/activerecord/test/cases/adapters/mysql2/transaction_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
@@ -46,7 +46,7 @@ module ActiveRecord
           Sample.transaction do
             s1.lock!
             barrier.wait
-            s2.update_attributes value: 1
+            s2.update value: 1
           end
         end
 
@@ -54,7 +54,7 @@ module ActiveRecord
           Sample.transaction do
             s2.lock!
             barrier.wait
-            s1.update_attributes value: 2
+            s1.update value: 2
           end
         ensure
           thread.join
diff --git a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
index b01f5d7f5a..97da96003d 100644
--- a/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/unsigned_type_test.rb
@@ -54,7 +54,7 @@ class Mysql2UnsignedTypeTest < ActiveRecord::Mysql2TestCase
     end
 
     @connection.columns("unsigned_types").select { |c| /^unsigned_/.match?(c.name) }.each do |column|
-      assert column.unsigned?
+      assert_predicate column, :unsigned?
     end
   end
 
diff --git a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
index 99c53dadeb..308ad1d854 100644
--- a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
@@ -62,6 +62,12 @@ class PostgresqlActiveSchemaTest < ActiveRecord::PostgreSQLTestCase
     expected = %(CREATE  INDEX  "index_people_on_last_name" ON "people" USING gist ("last_name" bpchar_pattern_ops))
     assert_equal expected, add_index(:people, :last_name, using: :gist, opclass: { last_name: :bpchar_pattern_ops })
 
+    expected = %(CREATE  INDEX  "index_people_on_last_name_and_first_name" ON "people"  ("last_name" DESC NULLS LAST, "first_name" ASC))
+    assert_equal expected, add_index(:people, [:last_name, :first_name], order: { last_name: "DESC NULLS LAST", first_name: :asc })
+
+    expected = %(CREATE  INDEX  "index_people_on_last_name" ON "people"  ("last_name" NULLS FIRST))
+    assert_equal expected, add_index(:people, :last_name, order: "NULLS FIRST")
+
     assert_raise ArgumentError do
       add_index(:people, :last_name, algorithm: :copy)
     end
diff --git a/activerecord/test/cases/adapters/postgresql/array_test.rb b/activerecord/test/cases/adapters/postgresql/array_test.rb
index 0e9e86f425..58fa7532a2 100644
--- a/activerecord/test/cases/adapters/postgresql/array_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/array_test.rb
@@ -39,12 +39,12 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
   def test_column
     assert_equal :string, @column.type
     assert_equal "character varying(255)", @column.sql_type
-    assert @column.array?
-    assert_not @type.binary?
+    assert_predicate @column, :array?
+    assert_not_predicate @type, :binary?
 
     ratings_column = PgArray.columns_hash["ratings"]
     assert_equal :integer, ratings_column.type
-    assert ratings_column.array?
+    assert_predicate ratings_column, :array?
   end
 
   def test_not_compatible_with_serialize_array
@@ -109,7 +109,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
 
     assert_equal :text, column.type
     assert_equal [], PgArray.column_defaults["snippets"]
-    assert column.array?
+    assert_predicate column, :array?
   end
 
   def test_change_column_cant_make_non_array_column_to_array
@@ -228,7 +228,9 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
 
   def test_insert_fixtures
     tag_values = ["val1", "val2", "val3_with_'_multiple_quote_'_chars"]
-    @connection.insert_fixtures([{ "tags" => tag_values }], "pg_arrays")
+    assert_deprecated do
+      @connection.insert_fixtures([{ "tags" => tag_values }], "pg_arrays")
+    end
     assert_equal(PgArray.last.tags, tag_values)
   end
 
@@ -255,7 +257,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     x = PgArray.create!(tags: tags)
     x.reload
 
-    refute x.changed?
+    assert_not_predicate x, :changed?
   end
 
   def test_quoting_non_standard_delimiters
@@ -277,7 +279,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     x.reload
 
     assert_equal %w(one two three), x.tags
-    assert_not x.changed?
+    assert_not_predicate x, :changed?
   end
 
   def test_mutate_value_in_array
@@ -288,7 +290,7 @@ class PostgresqlArrayTest < ActiveRecord::PostgreSQLTestCase
     x.reload
 
     assert_equal [{ "a" => "c" }, { "b" => "b" }], x.hstores
-    assert_not x.changed?
+    assert_not_predicate x, :changed?
   end
 
   def test_datetime_with_timezone_awareness
diff --git a/activerecord/test/cases/adapters/postgresql/bit_string_test.rb b/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
index df04299569..c8e728bbb6 100644
--- a/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bit_string_test.rb
@@ -29,20 +29,20 @@ class PostgresqlBitStringTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlBitString.columns_hash["a_bit"]
     assert_equal :bit, column.type
     assert_equal "bit(8)", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlBitString.type_for_attribute("a_bit")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_bit_string_varying_column
     column = PostgresqlBitString.columns_hash["a_bit_varying"]
     assert_equal :bit_varying, column.type
     assert_equal "bit varying(4)", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlBitString.type_for_attribute("a_bit_varying")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_default
diff --git a/activerecord/test/cases/adapters/postgresql/bytea_test.rb b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
index a6bee113ff..64bb6906cd 100644
--- a/activerecord/test/cases/adapters/postgresql/bytea_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/bytea_test.rb
@@ -75,7 +75,7 @@ class PostgresqlByteaTest < ActiveRecord::PostgreSQLTestCase
   def test_write_value
     data = "\u001F"
     record = ByteaDataType.create(payload: data)
-    assert_not record.new_record?
+    assert_not_predicate record, :new_record?
     assert_equal(data, record.payload)
   end
 
@@ -101,14 +101,14 @@ class PostgresqlByteaTest < ActiveRecord::PostgreSQLTestCase
     data = File.read(File.join(__dir__, "..", "..", "..", "assets", "example.log"))
     assert(data.size > 1)
     record = ByteaDataType.create(payload: data)
-    assert_not record.new_record?
+    assert_not_predicate record, :new_record?
     assert_equal(data, record.payload)
     assert_equal(data, ByteaDataType.where(id: record.id).first.payload)
   end
 
   def test_write_nil
     record = ByteaDataType.create(payload: nil)
-    assert_not record.new_record?
+    assert_not_predicate record, :new_record?
     assert_nil(record.payload)
     assert_nil(ByteaDataType.where(id: record.id).first.payload)
   end
diff --git a/activerecord/test/cases/adapters/postgresql/change_schema_test.rb b/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
index adf461a9cc..6dba4f3e14 100644
--- a/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/change_schema_test.rb
@@ -33,7 +33,7 @@ module ActiveRecord
         connection.change_column :strings, :somedate, :timestamp, array: true, cast_as: :timestamp
         column = connection.columns(:strings).find { |c| c.name == "somedate" }
         assert_equal :datetime, column.type
-        assert column.array?
+        assert_predicate column, :array?
       end
     end
   end
diff --git a/activerecord/test/cases/adapters/postgresql/citext_test.rb b/activerecord/test/cases/adapters/postgresql/citext_test.rb
index a25f102bad..9eb0b7d99c 100644
--- a/activerecord/test/cases/adapters/postgresql/citext_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/citext_test.rb
@@ -32,10 +32,10 @@ class PostgresqlCitextTest < ActiveRecord::PostgreSQLTestCase
     column = Citext.columns_hash["cival"]
     assert_equal :citext, column.type
     assert_equal "citext", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = Citext.type_for_attribute("cival")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_change_table_supports_json
diff --git a/activerecord/test/cases/adapters/postgresql/composite_test.rb b/activerecord/test/cases/adapters/postgresql/composite_test.rb
index 5da95f7e2c..b0ce2694a3 100644
--- a/activerecord/test/cases/adapters/postgresql/composite_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/composite_test.rb
@@ -51,10 +51,10 @@ class PostgresqlCompositeTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlComposite.columns_hash["address"]
     assert_nil column.type
     assert_equal "full_address", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlComposite.type_for_attribute("address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_composite_mapping
@@ -113,10 +113,10 @@ class PostgresqlCompositeWithCustomOIDTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlComposite.columns_hash["address"]
     assert_equal :full_address, column.type
     assert_equal "full_address", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlComposite.type_for_attribute("address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_composite_mapping
diff --git a/activerecord/test/cases/adapters/postgresql/connection_test.rb b/activerecord/test/cases/adapters/postgresql/connection_test.rb
index 81358b8fc4..d1b3c434e1 100644
--- a/activerecord/test/cases/adapters/postgresql/connection_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/connection_test.rb
@@ -157,7 +157,7 @@ module ActiveRecord
       original_connection_pid = @connection.query("select pg_backend_pid()")
 
       # Sanity check.
-      assert @connection.active?
+      assert_predicate @connection, :active?
 
       if @connection.send(:postgresql_version) >= 90200
         secondary_connection = ActiveRecord::Base.connection_pool.checkout
@@ -176,7 +176,7 @@ module ActiveRecord
 
       @connection.verify!
 
-      assert @connection.active?
+      assert_predicate @connection, :active?
 
       # If we get no exception here, then either we re-connected successfully, or
       # we never actually got disconnected.
diff --git a/activerecord/test/cases/adapters/postgresql/date_test.rb b/activerecord/test/cases/adapters/postgresql/date_test.rb
new file mode 100644
index 0000000000..a86abac2be
--- /dev/null
+++ b/activerecord/test/cases/adapters/postgresql/date_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/topic"
+
+class PostgresqlDateTest < ActiveRecord::PostgreSQLTestCase
+  def test_load_infinity_and_beyond
+    topic = Topic.find_by_sql("SELECT 'infinity'::date AS last_read").first
+    assert topic.last_read.infinite?, "timestamp should be infinite"
+    assert_operator topic.last_read, :>, 0
+
+    topic = Topic.find_by_sql("SELECT '-infinity'::date AS last_read").first
+    assert topic.last_read.infinite?, "timestamp should be infinite"
+    assert_operator topic.last_read, :<, 0
+  end
+
+  def test_save_infinity_and_beyond
+    topic = Topic.create!(last_read: 1.0 / 0.0)
+    assert_equal(1.0 / 0.0, topic.last_read)
+
+    topic = Topic.create!(last_read: -1.0 / 0.0)
+    assert_equal(-1.0 / 0.0, topic.last_read)
+  end
+
+  def test_bc_date
+    date = Date.new(0) - 1.week
+    topic = Topic.create!(last_read: date)
+    assert_equal date, Topic.find(topic.id).last_read
+  end
+
+  def test_bc_date_leap_year
+    date = Time.utc(-4, 2, 29).to_date
+    topic = Topic.create!(last_read: date)
+    assert_equal date, Topic.find(topic.id).last_read
+  end
+
+  def test_bc_date_year_zero
+    date = Time.utc(0, 4, 7).to_date
+    topic = Topic.create!(last_read: date)
+    assert_equal date, Topic.find(topic.id).last_read
+  end
+end
diff --git a/activerecord/test/cases/adapters/postgresql/domain_test.rb b/activerecord/test/cases/adapters/postgresql/domain_test.rb
index dafbc0a3db..eeaad94c27 100644
--- a/activerecord/test/cases/adapters/postgresql/domain_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/domain_test.rb
@@ -30,10 +30,10 @@ class PostgresqlDomainTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlDomain.columns_hash["price"]
     assert_equal :decimal, column.type
     assert_equal "custom_money", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlDomain.type_for_attribute("price")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_domain_acts_like_basetype
diff --git a/activerecord/test/cases/adapters/postgresql/enum_test.rb b/activerecord/test/cases/adapters/postgresql/enum_test.rb
index 3d3cbe11a3..6789ff63e7 100644
--- a/activerecord/test/cases/adapters/postgresql/enum_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/enum_test.rb
@@ -32,10 +32,10 @@ class PostgresqlEnumTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlEnum.columns_hash["current_mood"]
     assert_equal :enum, column.type
     assert_equal "mood", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlEnum.type_for_attribute("current_mood")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_enum_defaults
@@ -73,7 +73,7 @@ class PostgresqlEnumTest < ActiveRecord::PostgreSQLTestCase
     @connection.execute "INSERT INTO postgresql_enums VALUES (1, 'sad');"
     stderr_output = capture(:stderr) { PostgresqlEnum.first }
 
-    assert stderr_output.blank?
+    assert_predicate stderr_output, :blank?
   end
 
   def test_enum_type_cast
diff --git a/activerecord/test/cases/adapters/postgresql/foreign_table_test.rb b/activerecord/test/cases/adapters/postgresql/foreign_table_test.rb
new file mode 100644
index 0000000000..4fa315ad23
--- /dev/null
+++ b/activerecord/test/cases/adapters/postgresql/foreign_table_test.rb
@@ -0,0 +1,109 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/professor"
+
+if ActiveRecord::Base.connection.supports_foreign_tables?
+  class ForeignTableTest < ActiveRecord::TestCase
+    self.use_transactional_tests = false
+
+    class ForeignProfessor < ActiveRecord::Base
+      self.table_name = "foreign_professors"
+    end
+
+    class ForeignProfessorWithPk < ForeignProfessor
+      self.primary_key = "id"
+    end
+
+    def setup
+      @professor = Professor.create(name: "Nicola")
+
+      @connection = ActiveRecord::Base.connection
+      enable_extension!("postgres_fdw", @connection)
+
+      foreign_db_config = ARTest.connection_config["arunit2"]
+      @connection.execute <<-SQL
+        CREATE SERVER foreign_server
+          FOREIGN DATA WRAPPER postgres_fdw
+          OPTIONS (dbname '#{foreign_db_config["database"]}')
+      SQL
+
+      @connection.execute <<-SQL
+        CREATE USER MAPPING FOR CURRENT_USER
+          SERVER foreign_server
+      SQL
+
+      @connection.execute <<-SQL
+        CREATE FOREIGN TABLE foreign_professors (
+          id    int,
+          name  character varying NOT NULL
+        ) SERVER foreign_server OPTIONS (
+          table_name 'professors'
+        )
+      SQL
+    end
+
+    def teardown
+      disable_extension!("postgres_fdw", @connection)
+      @connection.execute <<-SQL
+        DROP SERVER IF EXISTS foreign_server CASCADE
+      SQL
+    end
+
+    def test_table_exists
+      table_name = ForeignProfessor.table_name
+      assert_not ActiveRecord::Base.connection.table_exists?(table_name)
+    end
+
+    def test_foreign_tables_are_valid_data_sources
+      table_name = ForeignProfessor.table_name
+      assert @connection.data_source_exists?(table_name), "'#{table_name}' should be a data source"
+    end
+
+    def test_foreign_tables
+      assert_equal ["foreign_professors"], @connection.foreign_tables
+    end
+
+    def test_foreign_table_exists
+      assert @connection.foreign_table_exists?("foreign_professors")
+      assert @connection.foreign_table_exists?(:foreign_professors)
+      assert_not @connection.foreign_table_exists?("nonexistingtable")
+      assert_not @connection.foreign_table_exists?("'")
+      assert_not @connection.foreign_table_exists?(nil)
+    end
+
+    def test_attribute_names
+      assert_equal ["id", "name"], ForeignProfessor.attribute_names
+    end
+
+    def test_attributes
+      professor = ForeignProfessorWithPk.find(@professor.id)
+      assert_equal @professor.attributes, professor.attributes
+    end
+
+    def test_does_not_have_a_primary_key
+      assert_nil ForeignProfessor.primary_key
+    end
+
+    def test_insert_record
+      # Explicit `id` here to avoid complex configurations to implicitly work with remote table
+      ForeignProfessorWithPk.create!(id: 100, name: "Leonardo")
+
+      professor = ForeignProfessorWithPk.last
+      assert_equal "Leonardo", professor.name
+    end
+
+    def test_update_record
+      professor = ForeignProfessorWithPk.find(@professor.id)
+      professor.name = "Albert"
+      professor.save!
+      professor.reload
+      assert_equal "Albert", professor.name
+    end
+
+    def test_delete_record
+      professor = ForeignProfessorWithPk.find(@professor.id)
+      assert_difference("ForeignProfessor.count", -1) { professor.destroy }
+    end
+  end
+end
diff --git a/activerecord/test/cases/adapters/postgresql/full_text_test.rb b/activerecord/test/cases/adapters/postgresql/full_text_test.rb
index c6f1e1727f..95dee3bf44 100644
--- a/activerecord/test/cases/adapters/postgresql/full_text_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/full_text_test.rb
@@ -22,10 +22,10 @@ class PostgresqlFullTextTest < ActiveRecord::PostgreSQLTestCase
     column = Tsvector.columns_hash["text_vector"]
     assert_equal :tsvector, column.type
     assert_equal "tsvector", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = Tsvector.type_for_attribute("text_vector")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_update_tsvector
diff --git a/activerecord/test/cases/adapters/postgresql/geometric_test.rb b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
index e1ba00e07b..8c6f046553 100644
--- a/activerecord/test/cases/adapters/postgresql/geometric_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/geometric_test.rb
@@ -39,10 +39,10 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlPoint.columns_hash["x"]
     assert_equal :point, column.type
     assert_equal "point", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlPoint.type_for_attribute("x")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_default
@@ -79,7 +79,7 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     p.reload
 
     assert_equal ActiveRecord::Point.new(10.0, 25.0), p.x
-    assert_not p.changed?
+    assert_not_predicate p, :changed?
   end
 
   def test_array_assignment
@@ -117,10 +117,10 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlPoint.columns_hash["legacy_x"]
     assert_equal :point, column.type
     assert_equal "point", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlPoint.type_for_attribute("legacy_x")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_legacy_default
@@ -157,7 +157,7 @@ class PostgresqlPointTest < ActiveRecord::PostgreSQLTestCase
     p.reload
 
     assert_equal [10.0, 25.0], p.legacy_x
-    assert_not p.changed?
+    assert_not_predicate p, :changed?
   end
 end
 
diff --git a/activerecord/test/cases/adapters/postgresql/hstore_test.rb b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
index f09e34b5f2..4b061a9375 100644
--- a/activerecord/test/cases/adapters/postgresql/hstore_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/hstore_test.rb
@@ -40,7 +40,7 @@ class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
   end
 
   def test_hstore_included_in_extensions
-    assert @connection.respond_to?(:extensions), "connection should have a list of extensions"
+    assert_respond_to @connection, :extensions
     assert_includes @connection.extensions, "hstore", "extension list should include hstore"
   end
 
@@ -58,9 +58,9 @@ class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
   def test_column
     assert_equal :hstore, @column.type
     assert_equal "hstore", @column.sql_type
-    assert_not @column.array?
+    assert_not_predicate @column, :array?
 
-    assert_not @type.binary?
+    assert_not_predicate @type, :binary?
   end
 
   def test_default
@@ -165,7 +165,7 @@ class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
     hstore.reload
 
     assert_equal "four", hstore.settings["three"]
-    assert_not hstore.changed?
+    assert_not_predicate hstore, :changed?
   end
 
   def test_dirty_from_user_equal
@@ -174,7 +174,7 @@ class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
 
     hstore.settings = { "key" => "value", "alongkey" => "anything" }
     assert_equal settings, hstore.settings
-    refute hstore.changed?
+    assert_not_predicate hstore, :changed?
   end
 
   def test_hstore_dirty_from_database_equal
@@ -184,7 +184,7 @@ class PostgresqlHstoreTest < ActiveRecord::PostgreSQLTestCase
 
     assert_equal settings, hstore.settings
     hstore.settings = settings
-    refute hstore.changed?
+    assert_not_predicate hstore, :changed?
   end
 
   def test_gen1
diff --git a/activerecord/test/cases/adapters/postgresql/infinity_test.rb b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
index 0b18c0c9d7..5e56ce8427 100644
--- a/activerecord/test/cases/adapters/postgresql/infinity_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/infinity_test.rb
@@ -13,6 +13,7 @@ class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
     @connection.create_table(:postgresql_infinities) do |t|
       t.float :float
       t.datetime :datetime
+      t.date :date
     end
   end
 
@@ -43,11 +44,25 @@ class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
   end
 
   test "type casting infinity on a datetime column" do
+    record = PostgresqlInfinity.create!(datetime: "infinity")
+    record.reload
+    assert_equal Float::INFINITY, record.datetime
+
     record = PostgresqlInfinity.create!(datetime: Float::INFINITY)
     record.reload
     assert_equal Float::INFINITY, record.datetime
   end
 
+  test "type casting infinity on a date column" do
+    record = PostgresqlInfinity.create!(date: "infinity")
+    record.reload
+    assert_equal Float::INFINITY, record.date
+
+    record = PostgresqlInfinity.create!(date: Float::INFINITY)
+    record.reload
+    assert_equal Float::INFINITY, record.date
+  end
+
   test "update_all with infinity on a datetime column" do
     record = PostgresqlInfinity.create!
     PostgresqlInfinity.update_all(datetime: Float::INFINITY)
@@ -68,4 +83,28 @@ class PostgresqlInfinityTest < ActiveRecord::PostgreSQLTestCase
       PostgresqlInfinity.reset_column_information
     end
   end
+
+  test "where clause with infinite range on a datetime column" do
+    record = PostgresqlInfinity.create!(datetime: Time.current)
+
+    string = PostgresqlInfinity.where(datetime: "-infinity".."infinity")
+    assert_equal record, string.take
+
+    infinity = PostgresqlInfinity.where(datetime: -::Float::INFINITY..::Float::INFINITY)
+    assert_equal record, infinity.take
+
+    assert_equal infinity.to_sql, string.to_sql
+  end
+
+  test "where clause with infinite range on a date column" do
+    record = PostgresqlInfinity.create!(date: Date.current)
+
+    string = PostgresqlInfinity.where(date: "-infinity".."infinity")
+    assert_equal record, string.take
+
+    infinity = PostgresqlInfinity.where(date: -::Float::INFINITY..::Float::INFINITY)
+    assert_equal record, infinity.take
+
+    assert_equal infinity.to_sql, string.to_sql
+  end
 end
diff --git a/activerecord/test/cases/adapters/postgresql/ltree_test.rb b/activerecord/test/cases/adapters/postgresql/ltree_test.rb
index eca29f2892..8349ee6ee2 100644
--- a/activerecord/test/cases/adapters/postgresql/ltree_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/ltree_test.rb
@@ -31,10 +31,10 @@ class PostgresqlLtreeTest < ActiveRecord::PostgreSQLTestCase
     column = Ltree.columns_hash["path"]
     assert_equal :ltree, column.type
     assert_equal "ltree", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = Ltree.type_for_attribute("path")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_write
diff --git a/activerecord/test/cases/adapters/postgresql/money_test.rb b/activerecord/test/cases/adapters/postgresql/money_test.rb
index cc10890fa8..be3590e8dd 100644
--- a/activerecord/test/cases/adapters/postgresql/money_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/money_test.rb
@@ -26,10 +26,10 @@ class PostgresqlMoneyTest < ActiveRecord::PostgreSQLTestCase
     assert_equal :money, column.type
     assert_equal "money", column.sql_type
     assert_equal 2, column.scale
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlMoney.type_for_attribute("wealth")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_default
diff --git a/activerecord/test/cases/adapters/postgresql/network_test.rb b/activerecord/test/cases/adapters/postgresql/network_test.rb
index f461544a85..736570451b 100644
--- a/activerecord/test/cases/adapters/postgresql/network_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/network_test.rb
@@ -24,30 +24,30 @@ class PostgresqlNetworkTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlNetworkAddress.columns_hash["cidr_address"]
     assert_equal :cidr, column.type
     assert_equal "cidr", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlNetworkAddress.type_for_attribute("cidr_address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_inet_column
     column = PostgresqlNetworkAddress.columns_hash["inet_address"]
     assert_equal :inet, column.type
     assert_equal "inet", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlNetworkAddress.type_for_attribute("inet_address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_macaddr_column
     column = PostgresqlNetworkAddress.columns_hash["mac_address"]
     assert_equal :macaddr, column.type
     assert_equal "macaddr", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = PostgresqlNetworkAddress.type_for_attribute("mac_address")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_network_types
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index 2c99fa78bd..7ad03c194f 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -532,6 +532,34 @@ class SchemaIndexOpclassTest < ActiveRecord::PostgreSQLTestCase
   end
 end
 
+class SchemaIndexNullsOrderTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+
+  setup do
+    @connection = ActiveRecord::Base.connection
+    @connection.create_table "trains" do |t|
+      t.string :name
+      t.text :description
+    end
+  end
+
+  teardown do
+    @connection.drop_table "trains", if_exists: true
+  end
+
+  def test_nulls_order_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_description ON trains USING btree(name NULLS FIRST, description)"
+    output = dump_table_schema "trains"
+    assert_match(/order: \{ name: "NULLS FIRST" \}/, output)
+  end
+
+  def test_non_default_order_with_nulls_is_dumped
+    @connection.execute "CREATE INDEX trains_name_and_desc ON trains USING btree(name DESC NULLS LAST, description)"
+    output = dump_table_schema "trains"
+    assert_match(/order: \{ name: "DESC NULLS LAST" \}/, output)
+  end
+end
+
 class DefaultsUsingMultipleSchemasAndDomainTest < ActiveRecord::PostgreSQLTestCase
   setup do
     @connection = ActiveRecord::Base.connection
diff --git a/activerecord/test/cases/adapters/postgresql/serial_test.rb b/activerecord/test/cases/adapters/postgresql/serial_test.rb
index 6a99323be5..83ea86be6d 100644
--- a/activerecord/test/cases/adapters/postgresql/serial_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/serial_test.rb
@@ -24,14 +24,14 @@ class PostgresqlSerialTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlSerial.columns_hash["seq"]
     assert_equal :integer, column.type
     assert_equal "integer", column.sql_type
-    assert column.serial?
+    assert_predicate column, :serial?
   end
 
   def test_not_serial_column
     column = PostgresqlSerial.columns_hash["serials_id"]
     assert_equal :integer, column.type
     assert_equal "integer", column.sql_type
-    assert_not column.serial?
+    assert_not_predicate column, :serial?
   end
 
   def test_schema_dump_with_shorthand
@@ -66,14 +66,14 @@ class PostgresqlBigSerialTest < ActiveRecord::PostgreSQLTestCase
     column = PostgresqlBigSerial.columns_hash["seq"]
     assert_equal :integer, column.type
     assert_equal "bigint", column.sql_type
-    assert column.serial?
+    assert_predicate column, :serial?
   end
 
   def test_not_bigserial_column
     column = PostgresqlBigSerial.columns_hash["serials_id"]
     assert_equal :integer, column.type
     assert_equal "bigint", column.sql_type
-    assert_not column.serial?
+    assert_not_predicate column, :serial?
   end
 
   def test_schema_dump_with_shorthand
@@ -111,7 +111,7 @@ module SequenceNameDetectionTestCases
       columns = @connection.columns(:foo)
       columns.each do |column|
         assert_equal :integer, column.type
-        assert column.serial?
+        assert_predicate column, :serial?
       end
     end
 
@@ -142,7 +142,7 @@ module SequenceNameDetectionTestCases
       columns = @connection.columns(@table_name)
       columns.each do |column|
         assert_equal :integer, column.type
-        assert column.serial?
+        assert_predicate column, :serial?
       end
     end
 
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index 9821b103df..8e952a9408 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -76,7 +76,7 @@ module ActiveRecord
             Sample.transaction do
               s1.lock!
               barrier.wait
-              s2.update_attributes value: 1
+              s2.update value: 1
             end
           end
 
@@ -84,7 +84,7 @@ module ActiveRecord
             Sample.transaction do
               s2.lock!
               barrier.wait
-              s1.update_attributes value: 2
+              s1.update value: 2
             end
           ensure
             thread.join
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index c24e0cb330..71d07e2f4c 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -82,7 +82,7 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
     UUIDType.reset_column_information
     column = UUIDType.columns_hash["thingy"]
 
-    assert column.array?
+    assert_predicate column, :array?
     assert_equal "{}", column.default
 
     schema = dump_table_schema "uuid_data_type"
@@ -93,10 +93,10 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
     column = UUIDType.columns_hash["guid"]
     assert_equal :uuid, column.type
     assert_equal "uuid", column.sql_type
-    assert_not column.array?
+    assert_not_predicate column, :array?
 
     type = UUIDType.type_for_attribute("guid")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_treat_blank_uuid_as_nil
@@ -178,7 +178,7 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
     duplicate = klass.new(guid: record.guid)
 
     assert record.guid.present? # Ensure we actually are testing a UUID
-    assert_not duplicate.valid?
+    assert_not_predicate duplicate, :valid?
   end
 end
 
diff --git a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
index 20579c6476..7e0ce3a28e 100644
--- a/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
+++ b/activerecord/test/cases/adapters/sqlite3/sqlite3_adapter_test.rb
@@ -475,11 +475,11 @@ module ActiveRecord
       end
 
       def test_respond_to_enable_extension
-        assert @conn.respond_to?(:enable_extension)
+        assert_respond_to @conn, :enable_extension
       end
 
       def test_respond_to_disable_extension
-        assert @conn.respond_to?(:disable_extension)
+        assert_respond_to @conn, :disable_extension
       end
 
       def test_statement_closed
diff --git a/activerecord/test/cases/ar_schema_test.rb b/activerecord/test/cases/ar_schema_test.rb
index 83974f327e..140d7cbcae 100644
--- a/activerecord/test/cases/ar_schema_test.rb
+++ b/activerecord/test/cases/ar_schema_test.rb
@@ -48,7 +48,7 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
 
     assert_nothing_raised { @connection.select_all "SELECT * FROM fruits" }
     assert_nothing_raised { @connection.select_all "SELECT * FROM schema_migrations" }
-    assert_equal 7, ActiveRecord::Migrator::current_version
+    assert_equal 7, @connection.migration_context.current_version
   end
 
   def test_schema_define_w_table_name_prefix
@@ -64,7 +64,7 @@ class ActiveRecordSchemaTest < ActiveRecord::TestCase
         t.column :flavor, :string
       end
     end
-    assert_equal 7, ActiveRecord::Migrator::current_version
+    assert_equal 7, @connection.migration_context.current_version
   ensure
     ActiveRecord::Base.table_name_prefix = old_table_name_prefix
     ActiveRecord::SchemaMigration.table_name = table_name
diff --git a/activerecord/test/cases/associations/belongs_to_associations_test.rb b/activerecord/test/cases/associations/belongs_to_associations_test.rb
index 0f7a249bf3..9e6d94191b 100644
--- a/activerecord/test/cases/associations/belongs_to_associations_test.rb
+++ b/activerecord/test/cases/associations/belongs_to_associations_test.rb
@@ -79,7 +79,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    assert account.valid?
+    assert_predicate account, :valid?
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
   end
@@ -95,7 +95,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    assert_not account.valid?
+    assert_not_predicate account, :valid?
     assert_equal [{ error: :blank }], account.errors.details[:company]
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
@@ -112,7 +112,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     end
 
     account = model.new
-    assert_not account.valid?
+    assert_not_predicate account, :valid?
     assert_equal [{ error: :blank }], account.errors.details[:company]
   ensure
     ActiveRecord::Base.belongs_to_required_by_default = original_value
@@ -246,14 +246,14 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     Firm.create("name" => "Apple")
     Client.create("name" => "Citibank", :firm_name => "Apple")
     citibank_result = Client.all.merge!(where: { name: "Citibank" }, includes: :firm_with_primary_key).first
-    assert citibank_result.association(:firm_with_primary_key).loaded?
+    assert_predicate citibank_result.association(:firm_with_primary_key), :loaded?
   end
 
   def test_eager_loading_with_primary_key_as_symbol
     Firm.create("name" => "Apple")
     Client.create("name" => "Citibank", :firm_name => "Apple")
     citibank_result = Client.all.merge!(where: { name: "Citibank" }, includes: :firm_with_primary_key_symbols).first
-    assert citibank_result.association(:firm_with_primary_key_symbols).loaded?
+    assert_predicate citibank_result.association(:firm_with_primary_key_symbols), :loaded?
   end
 
   def test_creating_the_belonging_object
@@ -320,7 +320,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     client  = Client.create!(name: "Jimmy")
     account = client.create_account!(credit_limit: 10)
     assert_equal account, client.account
-    assert account.persisted?
+    assert_predicate account, :persisted?
     client.save
     client.reload
     assert_equal account, client.account
@@ -330,7 +330,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     client = Client.create!(name: "Jimmy")
     assert_raise(ActiveRecord::RecordInvalid) { client.create_account! }
     assert_not_nil client.account
-    assert client.account.new_record?
+    assert_predicate client.account, :new_record?
   end
 
   def test_reloading_the_belonging_object
@@ -627,10 +627,10 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     final_cut = Client.new("name" => "Final Cut")
     firm = Firm.find(1)
     final_cut.firm = firm
-    assert !final_cut.persisted?
+    assert_not_predicate final_cut, :persisted?
     assert final_cut.save
-    assert final_cut.persisted?
-    assert firm.persisted?
+    assert_predicate final_cut, :persisted?
+    assert_predicate firm, :persisted?
     assert_equal firm, final_cut.firm
     final_cut.association(:firm).reload
     assert_equal firm, final_cut.firm
@@ -640,10 +640,10 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     final_cut = Client.new("name" => "Final Cut")
     firm = Firm.find(1)
     final_cut.firm_with_primary_key = firm
-    assert !final_cut.persisted?
+    assert_not_predicate final_cut, :persisted?
     assert final_cut.save
-    assert final_cut.persisted?
-    assert firm.persisted?
+    assert_predicate final_cut, :persisted?
+    assert_predicate firm, :persisted?
     assert_equal firm, final_cut.firm_with_primary_key
     final_cut.association(:firm_with_primary_key).reload
     assert_equal firm, final_cut.firm_with_primary_key
@@ -790,7 +790,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
 
   def test_cant_save_readonly_association
     assert_raise(ActiveRecord::ReadOnlyRecord) { companies(:first_client).readonly_firm.save! }
-    assert companies(:first_client).readonly_firm.readonly?
+    assert_predicate companies(:first_client).readonly_firm, :readonly?
   end
 
   def test_polymorphic_assignment_foreign_key_type_string
@@ -949,15 +949,15 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     firm_proxy                = client.send(:association_instance_get, :firm)
     firm_with_condition_proxy = client.send(:association_instance_get, :firm_with_condition)
 
-    assert !firm_proxy.stale_target?
-    assert !firm_with_condition_proxy.stale_target?
+    assert_not_predicate firm_proxy, :stale_target?
+    assert_not_predicate firm_with_condition_proxy, :stale_target?
     assert_equal companies(:first_firm), client.firm
     assert_equal companies(:first_firm), client.firm_with_condition
 
     client.client_of = companies(:another_firm).id
 
-    assert firm_proxy.stale_target?
-    assert firm_with_condition_proxy.stale_target?
+    assert_predicate firm_proxy, :stale_target?
+    assert_predicate firm_with_condition_proxy, :stale_target?
     assert_equal companies(:another_firm), client.firm
     assert_equal companies(:another_firm), client.firm_with_condition
   end
@@ -968,12 +968,12 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     sponsor.sponsorable
     proxy = sponsor.send(:association_instance_get, :sponsorable)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal members(:groucho), sponsor.sponsorable
 
     sponsor.sponsorable_id = members(:some_other_guy).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal members(:some_other_guy), sponsor.sponsorable
   end
 
@@ -983,12 +983,12 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     sponsor.sponsorable
     proxy = sponsor.send(:association_instance_get, :sponsorable)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal members(:groucho), sponsor.sponsorable
 
     sponsor.sponsorable_type = "Firm"
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal companies(:first_firm), sponsor.sponsorable
   end
 
@@ -1122,7 +1122,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     comment.post_id = 9223372036854775808 # out of range in the bigint
 
     assert_nil comment.post
-    assert_not comment.valid?
+    assert_not_predicate comment, :valid?
     assert_equal [{ error: :blank }], comment.errors.details[:post]
   end
 
@@ -1142,7 +1142,7 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
 
     citibank.firm_id = apple.id.to_s
 
-    assert !citibank.association(:firm).stale_target?
+    assert_not_predicate citibank.association(:firm), :stale_target?
   end
 
   def test_reflect_the_most_recent_change
diff --git a/activerecord/test/cases/associations/callbacks_test.rb b/activerecord/test/cases/associations/callbacks_test.rb
index e096cd4a0b..25d55dc4c9 100644
--- a/activerecord/test/cases/associations/callbacks_test.rb
+++ b/activerecord/test/cases/associations/callbacks_test.rb
@@ -15,7 +15,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     @david = authors(:david)
     @thinking = posts(:thinking)
     @authorless = posts(:authorless)
-    assert @david.post_log.empty?
+    assert_empty @david.post_log
   end
 
   def test_adding_macro_callbacks
@@ -96,7 +96,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
   def test_has_and_belongs_to_many_add_callback
     david = developers(:david)
     ar = projects(:active_record)
-    assert ar.developers_log.empty?
+    assert_empty ar.developers_log
     ar.developers_with_callbacks << david
     assert_equal ["before_adding#{david.id}", "after_adding#{david.id}"], ar.developers_log
     ar.developers_with_callbacks << david
@@ -122,12 +122,12 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     assert_equal alice, dev
     assert_not_nil new_dev
     assert new_dev, "record should not have been saved"
-    assert_not alice.new_record?
+    assert_not_predicate alice, :new_record?
   end
 
   def test_has_and_belongs_to_many_after_add_called_after_save
     ar = projects(:active_record)
-    assert ar.developers_log.empty?
+    assert_empty ar.developers_log
     alice = Developer.new(name: "alice")
     ar.developers_with_callbacks << alice
     assert_equal "after_adding#{alice.id}", ar.developers_log.last
@@ -143,7 +143,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     david = developers(:david)
     jamis = developers(:jamis)
     activerecord = projects(:active_record)
-    assert activerecord.developers_log.empty?
+    assert_empty activerecord.developers_log
     activerecord.developers_with_callbacks.delete(david)
     assert_equal ["before_removing#{david.id}", "after_removing#{david.id}"], activerecord.developers_log
 
@@ -154,7 +154,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
 
   def test_has_and_belongs_to_many_does_not_fire_callbacks_on_clear
     activerecord = projects(:active_record)
-    assert activerecord.developers_log.empty?
+    assert_empty activerecord.developers_log
     if activerecord.developers_with_callbacks.size == 0
       activerecord.developers << developers(:david)
       activerecord.developers << developers(:jamis)
@@ -163,7 +163,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
     end
     activerecord.developers_with_callbacks.flat_map { |d| ["before_removing#{d.id}", "after_removing#{d.id}"] }.sort
     assert activerecord.developers_with_callbacks.clear
-    assert_predicate activerecord.developers_log, :empty?
+    assert_empty activerecord.developers_log
   end
 
   def test_has_many_and_belongs_to_many_callbacks_for_save_on_parent
@@ -183,7 +183,7 @@ class AssociationCallbacksTest < ActiveRecord::TestCase
       @david.unchangeable_posts << @authorless
     rescue Exception
     end
-    assert @david.post_log.empty?
+    assert_empty @david.post_log
     assert_not_includes @david.unchangeable_posts, @authorless
     @david.reload
     assert_not_includes @david.unchangeable_posts, @authorless
diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 9830917bc3..cb07ca5cd3 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -284,7 +284,7 @@ class EagerAssociationTest < ActiveRecord::TestCase
   end
 
   def test_loading_from_an_association_that_has_a_hash_of_conditions
-    assert !Author.all.merge!(includes: :hello_posts_with_hash_conditions).find(authors(:david).id).hello_posts.empty?
+    assert_not_empty Author.all.merge!(includes: :hello_posts_with_hash_conditions).find(authors(:david).id).hello_posts
   end
 
   def test_loading_with_no_associations
@@ -1444,51 +1444,51 @@ class EagerAssociationTest < ActiveRecord::TestCase
   test "preloading readonly association" do
     # has-one
     firm = Firm.where(id: "1").preload(:readonly_account).first!
-    assert firm.readonly_account.readonly?
+    assert_predicate firm.readonly_account, :readonly?
 
     # has_and_belongs_to_many
     project = Project.where(id: "2").preload(:readonly_developers).first!
-    assert project.readonly_developers.first.readonly?
+    assert_predicate project.readonly_developers.first, :readonly?
 
     # has-many :through
     david = Author.where(id: "1").preload(:readonly_comments).first!
-    assert david.readonly_comments.first.readonly?
+    assert_predicate david.readonly_comments.first, :readonly?
   end
 
   test "eager-loading non-readonly association" do
     # has_one
     firm = Firm.where(id: "1").eager_load(:account).first!
-    assert_not firm.account.readonly?
+    assert_not_predicate firm.account, :readonly?
 
     # has_and_belongs_to_many
     project = Project.where(id: "2").eager_load(:developers).first!
-    assert_not project.developers.first.readonly?
+    assert_not_predicate project.developers.first, :readonly?
 
     # has_many :through
     david = Author.where(id: "1").eager_load(:comments).first!
-    assert_not david.comments.first.readonly?
+    assert_not_predicate david.comments.first, :readonly?
 
     # belongs_to
     post = Post.where(id: "1").eager_load(:author).first!
-    assert_not post.author.readonly?
+    assert_not_predicate post.author, :readonly?
   end
 
   test "eager-loading readonly association" do
     # has-one
     firm = Firm.where(id: "1").eager_load(:readonly_account).first!
-    assert firm.readonly_account.readonly?
+    assert_predicate firm.readonly_account, :readonly?
 
     # has_and_belongs_to_many
     project = Project.where(id: "2").eager_load(:readonly_developers).first!
-    assert project.readonly_developers.first.readonly?
+    assert_predicate project.readonly_developers.first, :readonly?
 
     # has-many :through
     david = Author.where(id: "1").eager_load(:readonly_comments).first!
-    assert david.readonly_comments.first.readonly?
+    assert_predicate david.readonly_comments.first, :readonly?
 
     # belongs_to
     post = Post.where(id: "1").eager_load(:readonly_author).first!
-    assert post.readonly_author.readonly?
+    assert_predicate post.readonly_author, :readonly?
   end
 
   test "preloading a polymorphic association with references to the associated table" do
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index c817d7267b..5f771fe85f 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -180,11 +180,11 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_has_and_belongs_to_many
     david = Developer.find(1)
 
-    assert !david.projects.empty?
+    assert_not_empty david.projects
     assert_equal 2, david.projects.size
 
     active_record = Project.find(1)
-    assert !active_record.developers.empty?
+    assert_not_empty active_record.developers
     assert_equal 3, active_record.developers.size
     assert_includes active_record.developers, david
   end
@@ -262,10 +262,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     no_of_projects = Project.count
     aredridel = Developer.new("name" => "Aredridel")
     aredridel.projects.concat([Project.find(1), p = Project.new("name" => "Projekt")])
-    assert !aredridel.persisted?
-    assert !p.persisted?
+    assert_not_predicate aredridel, :persisted?
+    assert_not_predicate p, :persisted?
     assert aredridel.save
-    assert aredridel.persisted?
+    assert_predicate aredridel, :persisted?
     assert_equal no_of_devels + 1, Developer.count
     assert_equal no_of_projects + 1, Project.count
     assert_equal 2, aredridel.projects.size
@@ -311,14 +311,14 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_build
     devel = Developer.find(1)
     proj = assert_no_queries(ignore_none: false) { devel.projects.build("name" => "Projekt") }
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
     assert_equal devel.projects.last, proj
-    assert devel.projects.loaded?
+    assert_predicate devel.projects, :loaded?
 
-    assert !proj.persisted?
+    assert_not_predicate proj, :persisted?
     devel.save
-    assert proj.persisted?
+    assert_predicate proj, :persisted?
     assert_equal devel.projects.last, proj
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
@@ -326,14 +326,14 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_new_aliased_to_build
     devel = Developer.find(1)
     proj = assert_no_queries(ignore_none: false) { devel.projects.new("name" => "Projekt") }
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
     assert_equal devel.projects.last, proj
-    assert devel.projects.loaded?
+    assert_predicate devel.projects, :loaded?
 
-    assert !proj.persisted?
+    assert_not_predicate proj, :persisted?
     devel.save
-    assert proj.persisted?
+    assert_predicate proj, :persisted?
     assert_equal devel.projects.last, proj
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
@@ -343,10 +343,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     devel.projects.build(name: "Make bed")
     proj2 = devel.projects.build(name: "Lie in it")
     assert_equal devel.projects.last, proj2
-    assert !proj2.persisted?
+    assert_not_predicate proj2, :persisted?
     devel.save
-    assert devel.persisted?
-    assert proj2.persisted?
+    assert_predicate devel, :persisted?
+    assert_predicate proj2, :persisted?
     assert_equal devel.projects.last, proj2
     assert_equal Developer.find_by_name("Marcel").projects.last, proj2  # prove join table is updated
   end
@@ -354,12 +354,12 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_create
     devel = Developer.find(1)
     proj = devel.projects.create("name" => "Projekt")
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
     assert_equal devel.projects.last, proj
-    assert !devel.projects.loaded?
+    assert_not_predicate devel.projects, :loaded?
 
-    assert proj.persisted?
+    assert_predicate proj, :persisted?
     assert_equal Developer.find(1).projects.sort_by(&:id).last, proj  # prove join table is updated
   end
 
@@ -367,14 +367,14 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     # in Oracle '' is saved as null therefore need to save ' ' in not null column
     post = categories(:general).post_with_conditions.build(body: " ")
 
-    assert        post.save
-    assert_equal  "Yet Another Testing Title", post.title
+    assert post.save
+    assert_equal "Yet Another Testing Title", post.title
 
     # in Oracle '' is saved as null therefore need to save ' ' in not null column
     another_post = categories(:general).post_with_conditions.create(body: " ")
 
-    assert        another_post.persisted?
-    assert_equal  "Yet Another Testing Title", another_post.title
+    assert_predicate another_post, :persisted?
+    assert_equal "Yet Another Testing Title", another_post.title
   end
 
   def test_distinct_after_the_fact
@@ -441,10 +441,10 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
 
   def test_removing_associations_on_destroy
     david = DeveloperWithBeforeDestroyRaise.find(1)
-    assert !david.projects.empty?
+    assert_not_empty david.projects
     david.destroy
-    assert david.projects.empty?
-    assert DeveloperWithBeforeDestroyRaise.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = 1").empty?
+    assert_empty david.projects
+    assert_empty DeveloperWithBeforeDestroyRaise.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = 1")
   end
 
   def test_destroying
@@ -459,7 +459,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
 
     join_records = Developer.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = #{david.id} AND project_id = #{project.id}")
-    assert join_records.empty?
+    assert_empty join_records
 
     assert_equal 1, david.reload.projects.size
     assert_equal 1, david.projects.reload.size
@@ -475,7 +475,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
 
     join_records = Developer.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = #{david.id}")
-    assert join_records.empty?
+    assert_empty join_records
 
     assert_equal 0, david.reload.projects.size
     assert_equal 0, david.projects.reload.size
@@ -484,23 +484,23 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
   def test_destroy_all
     david = Developer.find(1)
     david.projects.reload
-    assert !david.projects.empty?
+    assert_not_empty david.projects
 
     assert_no_difference "Project.count" do
       david.projects.destroy_all
     end
 
     join_records = Developer.connection.select_all("SELECT * FROM developers_projects WHERE developer_id = #{david.id}")
-    assert join_records.empty?
+    assert_empty join_records
 
-    assert david.projects.empty?
-    assert david.projects.reload.empty?
+    assert_empty david.projects
+    assert_empty david.projects.reload
   end
 
   def test_destroy_associations_destroys_multiple_associations
     george = parrots(:george)
-    assert !george.pirates.empty?
-    assert !george.treasures.empty?
+    assert_not_empty george.pirates
+    assert_not_empty george.treasures
 
     assert_no_difference "Pirate.count" do
       assert_no_difference "Treasure.count" do
@@ -509,12 +509,12 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     end
 
     join_records = Parrot.connection.select_all("SELECT * FROM parrots_pirates WHERE parrot_id = #{george.id}")
-    assert join_records.empty?
-    assert george.pirates.reload.empty?
+    assert_empty join_records
+    assert_empty george.pirates.reload
 
     join_records = Parrot.connection.select_all("SELECT * FROM parrots_treasures WHERE parrot_id = #{george.id}")
-    assert join_records.empty?
-    assert george.treasures.reload.empty?
+    assert_empty join_records
+    assert_empty george.treasures.reload
   end
 
   def test_associations_with_conditions
@@ -547,7 +547,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     developer = project.developers.first
 
     assert_no_queries(ignore_none: false) do
-      assert project.developers.loaded?
+      assert_predicate project.developers, :loaded?
       assert_includes project.developers, developer
     end
   end
@@ -557,18 +557,18 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     developer = project.developers.first
 
     project.reload
-    assert ! project.developers.loaded?
+    assert_not_predicate project.developers, :loaded?
     assert_queries(1) do
       assert_includes project.developers, developer
     end
-    assert ! project.developers.loaded?
+    assert_not_predicate project.developers, :loaded?
   end
 
   def test_include_returns_false_for_non_matching_record_to_verify_scoping
     project = projects(:active_record)
     developer = Developer.create name: "Bryan", salary: 50_000
 
-    assert ! project.developers.loaded?
+    assert_not_predicate project.developers, :loaded?
     assert ! project.developers.include?(developer)
   end
 
@@ -662,7 +662,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     assert_includes developer.sym_special_projects, sp
   end
 
-  def test_update_attributes_after_push_without_duplicate_join_table_rows
+  def test_update_columns_after_push_without_duplicate_join_table_rows
     developer = Developer.new("name" => "Kano")
     project = SpecialProject.create("name" => "Special Project")
     assert developer.save
@@ -763,9 +763,9 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
 
   def test_get_ids_for_unloaded_associations_does_not_load_them
     developer = developers(:david)
-    assert !developer.projects.loaded?
+    assert_not_predicate developer.projects, :loaded?
     assert_equal projects(:active_record, :action_controller).map(&:id).sort, developer.project_ids.sort
-    assert !developer.projects.loaded?
+    assert_not_predicate developer.projects, :loaded?
   end
 
   def test_assign_ids
diff --git a/activerecord/test/cases/associations/has_many_associations_test.rb b/activerecord/test/cases/associations/has_many_associations_test.rb
index 18548f8516..00821f2319 100644
--- a/activerecord/test/cases/associations/has_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_associations_test.rb
@@ -57,7 +57,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
 
   def test_custom_primary_key_on_new_record_should_fetch_with_query
     subscriber = Subscriber.new(nick: "webster132")
-    assert !subscriber.subscriptions.loaded?
+    assert_not_predicate subscriber.subscriptions, :loaded?
 
     assert_queries 1 do
       assert_equal 2, subscriber.subscriptions.size
@@ -68,7 +68,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
 
   def test_association_primary_key_on_new_record_should_fetch_with_query
     author = Author.new(name: "David")
-    assert !author.essays.loaded?
+    assert_not_predicate author.essays, :loaded?
 
     assert_queries 1 do
       assert_equal 1, author.essays.size
@@ -103,7 +103,7 @@ class HasManyAssociationsTestPrimaryKeys < ActiveRecord::TestCase
 
   def test_blank_custom_primary_key_on_new_record_should_not_run_queries
     author = Author.new
-    assert !author.essays.loaded?
+    assert_not_predicate author.essays, :loaded?
 
     assert_queries 0 do
       assert_equal 0, author.essays.size
@@ -201,7 +201,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     part.reload
 
     assert_nil part.ship
-    assert !part.updated_at_changed?
+    assert_not_predicate part, :updated_at_changed?
   end
 
   def test_create_from_association_should_respect_default_scope
@@ -444,7 +444,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       new_clients << company.clients_of_firm.build(name: "Another Client III")
     end
 
-    assert_not company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
     assert_queries(1) do
       assert_same new_clients[0], company.clients_of_firm.third
       assert_same new_clients[1], company.clients_of_firm.fourth
@@ -464,7 +464,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       new_clients << company.clients_of_firm.build(name: "Another Client III")
     end
 
-    assert_not company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
     assert_queries(1) do
       assert_same new_clients[0], company.clients_of_firm.third!
       assert_same new_clients[1], company.clients_of_firm.fourth!
@@ -587,14 +587,14 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     # taking from unloaded Relation
     bob = klass.find(authors(:bob).id)
     new_post = bob.posts.build
-    assert_not bob.posts.loaded?
+    assert_not_predicate bob.posts, :loaded?
     assert_equal [posts(:misc_by_bob)], bob.posts.take(1)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob)], bob.posts.take(2)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob), new_post], bob.posts.take(3)
 
     # taking from loaded Relation
     bob.posts.load
-    assert bob.posts.loaded?
+    assert_predicate bob.posts, :loaded?
     assert_equal [posts(:misc_by_bob)], bob.posts.take(1)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob)], bob.posts.take(2)
     assert_equal [posts(:misc_by_bob), posts(:other_by_bob), new_post], bob.posts.take(3)
@@ -713,13 +713,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_find_each
     firm = companies(:first_firm)
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries(4) do
       firm.clients.find_each(batch_size: 1) { |c| assert_equal firm.id, c.firm_id }
     end
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_find_each_with_conditions
@@ -732,13 +732,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_find_in_batches
     firm = companies(:first_firm)
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries(2) do
       firm.clients.find_in_batches(batch_size: 2) do |clients|
@@ -746,7 +746,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_find_all_sanitized
@@ -955,20 +955,20 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_new_aliased_to_build
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.new("name" => "Another Client") }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     assert_equal "Another Client", new_client.name
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal new_client, company.clients_of_firm.last
   end
 
   def test_build
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build("name" => "Another Client") }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     assert_equal "Another Client", new_client.name
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal new_client, company.clients_of_firm.last
   end
 
@@ -982,9 +982,9 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   def test_collection_not_empty_after_building
     company = companies(:first_firm)
-    assert_predicate company.contracts, :empty?
+    assert_empty company.contracts
     company.contracts.build
-    assert_not_predicate company.contracts, :empty?
+    assert_not_empty company.contracts
   end
 
   def test_collection_size_twice_for_regressions
@@ -1008,7 +1008,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_build_followed_by_save_does_not_load_target
     companies(:first_firm).clients_of_firm.build("name" => "Another Client")
     assert companies(:first_firm).save
-    assert !companies(:first_firm).clients_of_firm.loaded?
+    assert_not_predicate companies(:first_firm).clients_of_firm, :loaded?
   end
 
   def test_build_without_loading_association
@@ -1028,10 +1028,10 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_build_via_block
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build { |client| client.name = "Another Client" } }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     assert_equal "Another Client", new_client.name
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal new_client, company.clients_of_firm.last
   end
 
@@ -1069,7 +1069,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_predicate companies(:first_firm).clients_of_firm, :loaded?
 
     new_client = companies(:first_firm).clients_of_firm.create("name" => "Another Client")
-    assert new_client.persisted?
+    assert_predicate new_client, :persisted?
     assert_equal new_client, companies(:first_firm).clients_of_firm.last
     assert_equal new_client, companies(:first_firm).clients_of_firm.reload.last
   end
@@ -1082,7 +1082,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_create_followed_by_save_does_not_load_target
     companies(:first_firm).clients_of_firm.create("name" => "Another Client")
     assert companies(:first_firm).save
-    assert !companies(:first_firm).clients_of_firm.loaded?
+    assert_not_predicate companies(:first_firm).clients_of_firm, :loaded?
   end
 
   def test_deleting
@@ -1108,7 +1108,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     # option is not given on the association.
     ship = Ship.create(name: "Countless", treasures_count: 10)
 
-    assert_not Ship.reflect_on_association(:treasures).has_cached_counter?
+    assert_not_predicate Ship.reflect_on_association(:treasures), :has_cached_counter?
 
     # Count should come from sql count() of treasures rather than treasures_count attribute
     assert_equal ship.treasures.size, 0
@@ -1199,7 +1199,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_empty_with_counter_cache
     post = posts(:welcome)
     assert_queries(0) do
-      assert_not post.comments.empty?
+      assert_not_empty post.comments
     end
   end
 
@@ -1211,20 +1211,20 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     end
   end
 
-  def test_calling_update_attributes_on_id_changes_the_counter_cache
+  def test_calling_update_on_id_changes_the_counter_cache
     topic = Topic.order("id ASC").first
     original_count = topic.replies.to_a.size
     assert_equal original_count, topic.replies_count
 
     first_reply = topic.replies.first
-    first_reply.update_attributes(parent_id: nil)
+    first_reply.update(parent_id: nil)
     assert_equal original_count - 1, topic.reload.replies_count
 
-    first_reply.update_attributes(parent_id: topic.id)
+    first_reply.update(parent_id: topic.id)
     assert_equal original_count, topic.reload.replies_count
   end
 
-  def test_calling_update_attributes_changing_ids_doesnt_change_counter_cache
+  def test_calling_update_changing_ids_doesnt_change_counter_cache
     topic1 = Topic.find(1)
     topic2 = Topic.find(3)
     original_count1 = topic1.replies.to_a.size
@@ -1233,11 +1233,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     reply1 = topic1.replies.first
     reply2 = topic2.replies.first
 
-    reply1.update_attributes(parent_id: topic2.id)
+    reply1.update(parent_id: topic2.id)
     assert_equal original_count1 - 1, topic1.reload.replies_count
     assert_equal original_count2 + 1, topic2.reload.replies_count
 
-    reply2.update_attributes(parent_id: topic1.id)
+    reply2.update(parent_id: topic1.id)
     assert_equal original_count1, topic1.reload.replies_count
     assert_equal original_count2, topic2.reload.replies_count
   end
@@ -1441,13 +1441,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_creation_respects_hash_condition
     ms_client = companies(:first_firm).clients_like_ms_with_hash_conditions.build
 
-    assert        ms_client.save
-    assert_equal  "Microsoft", ms_client.name
+    assert ms_client.save
+    assert_equal "Microsoft", ms_client.name
 
     another_ms_client = companies(:first_firm).clients_like_ms_with_hash_conditions.create
 
-    assert        another_ms_client.persisted?
-    assert_equal  "Microsoft", another_ms_client.name
+    assert_predicate another_ms_client, :persisted?
+    assert_equal "Microsoft", another_ms_client.name
   end
 
   def test_clearing_without_initial_access
@@ -1570,7 +1570,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = companies(:first_firm)
     assert_equal 3, firm.clients.size
     firm.destroy
-    assert Client.all.merge!(where: "firm_id=#{firm.id}").to_a.empty?
+    assert_empty Client.all.merge!(where: "firm_id=#{firm.id}").to_a
   end
 
   def test_dependence_for_associations_with_hash_condition
@@ -1633,7 +1633,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = RestrictedWithExceptionFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
 
-    assert !firm.companies.empty?
+    assert_not_empty firm.companies
     assert_raise(ActiveRecord::DeleteRestrictionError) { firm.destroy }
     assert RestrictedWithExceptionFirm.exists?(name: "restrict")
     assert firm.companies.exists?(name: "child")
@@ -1643,11 +1643,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = RestrictedWithErrorFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
 
-    assert !firm.companies.empty?
+    assert_not_empty firm.companies
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
 
     assert_equal "Cannot delete record because dependent companies exist", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
@@ -1660,11 +1660,11 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm = RestrictedWithErrorFirm.create!(name: "restrict")
     firm.companies.create(name: "child")
 
-    assert !firm.companies.empty?
+    assert_not_empty firm.companies
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
 
     assert_equal "Cannot delete record because dependent client companies exist", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
@@ -1716,8 +1716,8 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     account = Account.new
     orig_accounts = firm.accounts.to_a
 
-    assert !account.valid?
-    assert !orig_accounts.empty?
+    assert_not_predicate account, :valid?
+    assert_not_empty orig_accounts
     error = assert_raise ActiveRecord::RecordNotSaved do
       firm.accounts = [account]
     end
@@ -1775,9 +1775,9 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   def test_get_ids_for_unloaded_associations_does_not_load_them
     company = companies(:first_firm)
-    assert !company.clients.loaded?
+    assert_not_predicate company.clients, :loaded?
     assert_equal [companies(:first_client).id, companies(:second_client).id, companies(:another_first_firm_client).id], company.client_ids
-    assert !company.clients.loaded?
+    assert_not_predicate company.clients, :loaded?
   end
 
   def test_counter_cache_on_unloaded_association
@@ -1842,6 +1842,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     ].each { |block| assert_raise(ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection, &block) }
   end
 
+  def test_associations_order_should_be_priority_over_throughs_order
+    david = authors(:david)
+    expected = [12, 10, 9, 8, 7, 6, 5, 3, 2, 1]
+    assert_equal expected, david.comments_desc.map(&:id)
+    assert_equal expected, Author.includes(:comments_desc).find(david.id).comments_desc.map(&:id)
+  end
+
   def test_dynamic_find_should_respect_association_order_for_through
     assert_equal Comment.find(10), authors(:david).comments_desc.where("comments.type = 'SpecialComment'").first
     assert_equal Comment.find(10), authors(:david).comments_desc.find_by_type("SpecialComment")
@@ -1859,7 +1866,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     client = firm.clients.first
 
     assert_no_queries do
-      assert firm.clients.loaded?
+      assert_predicate firm.clients, :loaded?
       assert_equal true, firm.clients.include?(client)
     end
   end
@@ -1869,18 +1876,18 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     client = firm.clients.first
 
     firm.reload
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
     assert_queries(1) do
       assert_equal true, firm.clients.include?(client)
     end
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_include_returns_false_for_non_matching_record_to_verify_scoping
     firm = companies(:first_firm)
     client = Client.create!(name: "Not Associated")
 
-    assert ! firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
     assert_equal false, firm.clients.include?(client)
   end
 
@@ -1889,13 +1896,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     firm.clients.first
     firm.clients.second
     firm.clients.last
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_first_or_last_on_loaded_association_should_not_fetch_with_query
     firm = companies(:first_firm)
     firm.clients.load_target
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
 
     assert_no_queries(ignore_none: false) do
       firm.clients.first
@@ -1908,7 +1915,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_first_or_last_on_existing_record_with_build_should_load_association
     firm = companies(:first_firm)
     firm.clients.build(name: "Foo")
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries 1 do
       firm.clients.first
@@ -1916,13 +1923,13 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.last
     end
 
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_first_nth_or_last_on_existing_record_with_create_should_not_load_association
     firm = companies(:first_firm)
     firm.clients.create(name: "Foo")
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries 3 do
       firm.clients.first
@@ -1930,7 +1937,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.last
     end
 
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_first_nth_or_last_on_new_record_should_not_run_queries
@@ -1946,14 +1953,14 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
   def test_calling_first_or_last_with_integer_on_association_should_not_load_association
     firm = companies(:first_firm)
     firm.clients.create(name: "Foo")
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
 
     assert_queries 2 do
       firm.clients.first(2)
       firm.clients.last(2)
     end
 
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_many_should_count_instead_of_loading_association
@@ -1961,7 +1968,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_queries(1) do
       firm.clients.many?  # use count query
     end
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_many_on_loaded_association_should_not_use_query
@@ -1976,22 +1983,22 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.expects(:size).never
       firm.clients.many? { true }
     end
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_many_should_return_false_if_none_or_one
     firm = companies(:another_firm)
-    assert !firm.clients_like_ms.many?
+    assert_not_predicate firm.clients_like_ms, :many?
     assert_equal 0, firm.clients_like_ms.size
 
     firm = companies(:first_firm)
-    assert !firm.limited_clients.many?
+    assert_not_predicate firm.limited_clients, :many?
     assert_equal 1, firm.limited_clients.size
   end
 
   def test_calling_many_should_return_true_if_more_than_one
     firm = companies(:first_firm)
-    assert firm.clients.many?
+    assert_predicate firm.clients, :many?
     assert_equal 3, firm.clients.size
   end
 
@@ -2000,7 +2007,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_queries(1) do
       firm.clients.none?  # use count query
     end
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_none_on_loaded_association_should_not_use_query
@@ -2015,18 +2022,18 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.expects(:size).never
       firm.clients.none? { true }
     end
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_none_should_return_true_if_none
     firm = companies(:another_firm)
-    assert firm.clients_like_ms.none?
+    assert_predicate firm.clients_like_ms, :none?
     assert_equal 0, firm.clients_like_ms.size
   end
 
   def test_calling_none_should_return_false_if_any
     firm = companies(:first_firm)
-    assert !firm.limited_clients.none?
+    assert_not_predicate firm.limited_clients, :none?
     assert_equal 1, firm.limited_clients.size
   end
 
@@ -2035,7 +2042,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_queries(1) do
       firm.clients.one?  # use count query
     end
-    assert !firm.clients.loaded?
+    assert_not_predicate firm.clients, :loaded?
   end
 
   def test_calling_one_on_loaded_association_should_not_use_query
@@ -2050,24 +2057,24 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
       firm.clients.expects(:size).never
       firm.clients.one? { true }
     end
-    assert firm.clients.loaded?
+    assert_predicate firm.clients, :loaded?
   end
 
   def test_calling_one_should_return_false_if_zero
     firm = companies(:another_firm)
-    assert ! firm.clients_like_ms.one?
+    assert_not_predicate firm.clients_like_ms, :one?
     assert_equal 0, firm.clients_like_ms.size
   end
 
   def test_calling_one_should_return_true_if_one
     firm = companies(:first_firm)
-    assert firm.limited_clients.one?
+    assert_predicate firm.limited_clients, :one?
     assert_equal 1, firm.limited_clients.size
   end
 
   def test_calling_one_should_return_false_if_more_than_one
     firm = companies(:first_firm)
-    assert ! firm.clients.one?
+    assert_not_predicate firm.clients, :one?
     assert_equal 3, firm.clients.size
   end
 
@@ -2287,7 +2294,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     post = posts(:welcome)
 
     assert post.taggings_with_delete_all.count > 0
-    assert !post.taggings_with_delete_all.loaded?
+    assert_not_predicate post.taggings_with_delete_all, :loaded?
 
     # 2 queries: one DELETE and another to update the counter cache
     assert_queries(2) do
@@ -2309,7 +2316,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
 
   test "collection proxy respects default scope" do
     author = authors(:mary)
-    assert !author.first_posts.exists?
+    assert_not_predicate author.first_posts, :exists?
   end
 
   test "association with extend option" do
@@ -2428,7 +2435,7 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     pirate = FamousPirate.new
     pirate.famous_ships << ship = FamousShip.new
 
-    assert pirate.valid?
+    assert_predicate pirate, :valid?
     assert_not pirate.valid?(:conference)
     assert_equal "can't be blank", ship.errors[:name].first
   end
diff --git a/activerecord/test/cases/associations/has_many_through_associations_test.rb b/activerecord/test/cases/associations/has_many_through_associations_test.rb
index 56a4b7c4d1..3b3d4037b9 100644
--- a/activerecord/test/cases/associations/has_many_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -46,6 +46,11 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     Reader.create person_id: 0, post_id: 0
   end
 
+  def test_marshal_dump
+    preloaded = Post.includes(:first_blue_tags).first
+    assert_equal preloaded, Marshal.load(Marshal.dump(preloaded))
+  end
+
   def test_preload_sti_rhs_class
     developers = Developer.includes(:firms).all.to_a
     assert_no_queries do
@@ -353,10 +358,10 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
 
     assert_queries(1) do
-      assert posts(:welcome).people.empty?
+      assert_empty posts(:welcome).people
     end
 
-    assert posts(:welcome).reload.people.reload.empty?
+    assert_empty posts(:welcome).reload.people.reload
   end
 
   def test_destroy_association
@@ -366,8 +371,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert posts(:welcome).reload.people.empty?
-    assert posts(:welcome).people.reload.empty?
+    assert_empty posts(:welcome).reload.people
+    assert_empty posts(:welcome).people.reload
   end
 
   def test_destroy_all
@@ -377,8 +382,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       end
     end
 
-    assert posts(:welcome).reload.people.empty?
-    assert posts(:welcome).people.reload.empty?
+    assert_empty posts(:welcome).reload.people
+    assert_empty posts(:welcome).people.reload
   end
 
   def test_should_raise_exception_for_destroying_mismatching_records
@@ -538,6 +543,16 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_update_counter_caches_on_destroy_with_indestructible_through_record
+    post = posts(:welcome)
+    tag  = post.indestructible_tags.create!(name: "doomed")
+    post.update_columns(indestructible_tags_count: post.indestructible_tags.count)
+
+    assert_no_difference "post.reload.indestructible_tags_count" do
+      posts(:welcome).indestructible_tags.destroy(tag)
+    end
+  end
+
   def test_replace_association
     assert_queries(4) { posts(:welcome);people(:david);people(:michael); posts(:welcome).people.reload }
 
@@ -675,10 +690,10 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     end
 
     assert_queries(0) do
-      assert posts(:welcome).people.empty?
+      assert_empty posts(:welcome).people
     end
 
-    assert posts(:welcome).reload.people.reload.empty?
+    assert_empty posts(:welcome).reload.people.reload
   end
 
   def test_association_callback_ordering
@@ -760,9 +775,9 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
 
   def test_get_ids_for_unloaded_associations_does_not_load_them
     person = people(:michael)
-    assert !person.posts.loaded?
+    assert_not_predicate person.posts, :loaded?
     assert_equal [posts(:welcome).id, posts(:authorless).id].sort, person.post_ids.sort
-    assert !person.posts.loaded?
+    assert_not_predicate person.posts, :loaded?
   end
 
   def test_association_proxy_transaction_method_starts_transaction_in_association_class
@@ -852,7 +867,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     category = author.named_categories.create(name: "Primary")
     author.named_categories.delete(category)
     assert !Categorization.exists?(author_id: author.id, named_category_name: category.name)
-    assert author.named_categories.reload.empty?
+    assert_empty author.named_categories.reload
   end
 
   def test_collection_singular_ids_getter_with_string_primary_keys
@@ -934,8 +949,8 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_through_association_readonly_should_be_false
-    assert !people(:michael).posts.first.readonly?
-    assert !people(:michael).posts.to_a.first.readonly?
+    assert_not_predicate people(:michael).posts.first, :readonly?
+    assert_not_predicate people(:michael).posts.to_a.first, :readonly?
   end
 
   def test_can_update_through_association
@@ -1024,12 +1039,12 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     post.author_categorizations
     proxy = post.send(:association_instance_get, :author_categorizations)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal authors(:mary).categorizations.sort_by(&:id), post.author_categorizations.sort_by(&:id)
 
     post.author_id = authors(:david).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal authors(:david).categorizations.sort_by(&:id), post.author_categorizations.sort_by(&:id)
   end
 
@@ -1046,7 +1061,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
 
     assert_includes post.author_addresses, address
     post.author_addresses.delete(address)
-    assert post[:author_count].nil?
+    assert_predicate post[:author_count], :nil?
   end
 
   def test_primary_key_option_on_source
diff --git a/activerecord/test/cases/associations/has_one_associations_test.rb b/activerecord/test/cases/associations/has_one_associations_test.rb
index ec5d95080b..1a213ef7e4 100644
--- a/activerecord/test/cases/associations/has_one_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_associations_test.rb
@@ -114,8 +114,8 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     developer = Developer.create!(name: "Someone")
     ship = Ship.create!(name: "Planet Caravan", developer: developer)
     ship.destroy
-    assert !ship.persisted?
-    assert !developer.persisted?
+    assert_not_predicate ship, :persisted?
+    assert_not_predicate developer, :persisted?
   end
 
   def test_natural_assignment_to_nil_after_destroy
@@ -186,7 +186,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     assert_raise(ActiveRecord::DeleteRestrictionError) { firm.destroy }
     assert RestrictedWithExceptionFirm.exists?(name: "restrict")
-    assert firm.account.present?
+    assert_predicate firm.account, :present?
   end
 
   def test_restrict_with_error
@@ -197,10 +197,10 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
     assert_equal "Cannot delete record because a dependent account exists", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
-    assert firm.account.present?
+    assert_predicate firm.account, :present?
   end
 
   def test_restrict_with_error_with_locale
@@ -213,10 +213,10 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
     firm.destroy
 
-    assert !firm.errors.empty?
+    assert_not_empty firm.errors
     assert_equal "Cannot delete record because a dependent firm account exists", firm.errors[:base].first
     assert RestrictedWithErrorFirm.exists?(name: "restrict")
-    assert firm.account.present?
+    assert_predicate firm.account, :present?
   ensure
     I18n.backend.reload!
   end
@@ -377,7 +377,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
   def test_assignment_before_child_saved
     firm = Firm.find(1)
     firm.account = a = Account.new("credit_limit" => 1000)
-    assert a.persisted?
+    assert_predicate a, :persisted?
     assert_equal a, firm.account
     assert_equal a, firm.account
     firm.association(:account).reload
@@ -395,7 +395,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
   def test_cant_save_readonly_association
     assert_raise(ActiveRecord::ReadOnlyRecord) { companies(:first_firm).readonly_account.save!  }
-    assert companies(:first_firm).readonly_account.readonly?
+    assert_predicate companies(:first_firm).readonly_account, :readonly?
   end
 
   def test_has_one_proxy_should_not_respond_to_private_methods
@@ -433,7 +433,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
 
   def test_create_respects_hash_condition
     account = companies(:first_firm).create_account_limit_500_with_hash_conditions
-    assert       account.persisted?
+    assert_predicate account, :persisted?
     assert_equal 500, account.credit_limit
   end
 
@@ -450,7 +450,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     new_ship = pirate.create_ship
     assert_not_equal ships(:black_pearl), new_ship
     assert_equal new_ship, pirate.ship
-    assert new_ship.new_record?
+    assert_predicate new_ship, :new_record?
     assert_nil orig_ship.pirate_id
     assert !orig_ship.changed? # check it was saved
   end
@@ -460,8 +460,8 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     orig_ship = pirate.dependent_ship
 
     new_ship = pirate.create_dependent_ship
-    assert new_ship.new_record?
-    assert orig_ship.destroyed?
+    assert_predicate new_ship, :new_record?
+    assert_predicate orig_ship, :destroyed?
   end
 
   def test_creation_failure_due_to_new_record_should_raise_error
@@ -481,7 +481,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     pirate = pirates(:blackbeard)
     pirate.ship.name = nil
 
-    assert !pirate.ship.valid?
+    assert_not_predicate pirate.ship, :valid?
     error = assert_raise(ActiveRecord::RecordNotSaved) do
       pirate.ship = ships(:interceptor)
     end
@@ -588,7 +588,7 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     ship.save!
 
     ship.name = "new name"
-    assert ship.changed?
+    assert_predicate ship, :changed?
     assert_queries(1) do
       # One query for updating name, not triggering query for updating pirate_id
       pirate.ship = ship
diff --git a/activerecord/test/cases/associations/has_one_through_associations_test.rb b/activerecord/test/cases/associations/has_one_through_associations_test.rb
index 1d37457464..9964f084ac 100644
--- a/activerecord/test/cases/associations/has_one_through_associations_test.rb
+++ b/activerecord/test/cases/associations/has_one_through_associations_test.rb
@@ -42,6 +42,18 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
     assert_not_nil new_member.club
   end
 
+  def test_creating_association_builds_through_record
+    new_member = Member.create(name: "Chris")
+    new_club = new_member.association(:club).build
+    assert new_member.current_membership
+    assert_equal new_club, new_member.club
+    assert_predicate new_club, :new_record?
+    assert_predicate new_member.current_membership, :new_record?
+    assert new_member.save
+    assert_predicate new_club, :persisted?
+    assert_predicate new_member.current_membership, :persisted?
+  end
+
   def test_creating_association_builds_through_record_for_new
     new_member = Member.new(name: "Jane")
     new_member.club = clubs(:moustache_club)
@@ -229,7 +241,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
       MemberDetail.all.merge!(includes: :member_type).to_a
     end
     @new_detail = @member_details[0]
-    assert @new_detail.send(:association, :member_type).loaded?
+    assert_predicate @new_detail.send(:association, :member_type), :loaded?
     assert_no_queries { @new_detail.member_type }
   end
 
@@ -317,12 +329,12 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
     minivan.dashboard
     proxy = minivan.send(:association_instance_get, :dashboard)
 
-    assert !proxy.stale_target?
+    assert_not_predicate proxy, :stale_target?
     assert_equal dashboards(:cool_first), minivan.dashboard
 
     minivan.speedometer_id = speedometers(:second).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal dashboards(:second), minivan.dashboard
   end
 
@@ -334,7 +346,7 @@ class HasOneThroughAssociationsTest < ActiveRecord::TestCase
 
     minivan.speedometer_id = speedometers(:second).id
 
-    assert proxy.stale_target?
+    assert_predicate proxy, :stale_target?
     assert_equal dashboards(:second), minivan.dashboard
   end
 
diff --git a/activerecord/test/cases/associations/inner_join_association_test.rb b/activerecord/test/cases/associations/inner_join_association_test.rb
index 7be875fec6..ca0620dc3b 100644
--- a/activerecord/test/cases/associations/inner_join_association_test.rb
+++ b/activerecord/test/cases/associations/inner_join_association_test.rb
@@ -115,19 +115,19 @@ class InnerJoinAssociationTest < ActiveRecord::TestCase
     scope = Post.joins(:special_comments).where(id: posts(:sti_comments).id)
 
     # The join should match SpecialComment and its subclasses only
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
-    assert !scope.where("comments.type" => "SubSpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
+    assert_not_empty scope.where("comments.type" => "SubSpecialComment")
   end
 
   def test_find_with_conditions_on_reflection
-    assert !posts(:welcome).comments.empty?
+    assert_not_empty posts(:welcome).comments
     assert Post.joins(:nonexistent_comments).where(id: posts(:welcome).id).empty? # [sic!]
   end
 
   def test_find_with_conditions_on_through_reflection
-    assert !posts(:welcome).tags.empty?
-    assert Post.joins(:misc_tags).where(id: posts(:welcome).id).empty?
+    assert_not_empty posts(:welcome).tags
+    assert_empty Post.joins(:misc_tags).where(id: posts(:welcome).id)
   end
 
   test "the default scope of the target is applied when joining associations" do
diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index c0d328ca8a..bad1bcdb67 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -129,7 +129,7 @@ class AutomaticInverseFindingTests < ActiveRecord::TestCase
   def test_polymorphic_has_one_should_find_inverse_automatically
     man_reflection = Man.reflect_on_association(:polymorphic_face_without_inverse)
 
-    assert man_reflection.has_inverse?
+    assert_predicate man_reflection, :has_inverse?
   end
 end
 
@@ -150,22 +150,22 @@ class InverseAssociationTests < ActiveRecord::TestCase
 
   def test_should_be_able_to_ask_a_reflection_if_it_has_an_inverse
     has_one_with_inverse_ref = Man.reflect_on_association(:face)
-    assert has_one_with_inverse_ref.has_inverse?
+    assert_predicate has_one_with_inverse_ref, :has_inverse?
 
     has_many_with_inverse_ref = Man.reflect_on_association(:interests)
-    assert has_many_with_inverse_ref.has_inverse?
+    assert_predicate has_many_with_inverse_ref, :has_inverse?
 
     belongs_to_with_inverse_ref = Face.reflect_on_association(:man)
-    assert belongs_to_with_inverse_ref.has_inverse?
+    assert_predicate belongs_to_with_inverse_ref, :has_inverse?
 
     has_one_without_inverse_ref = Club.reflect_on_association(:sponsor)
-    assert !has_one_without_inverse_ref.has_inverse?
+    assert_not_predicate has_one_without_inverse_ref, :has_inverse?
 
     has_many_without_inverse_ref = Club.reflect_on_association(:memberships)
-    assert !has_many_without_inverse_ref.has_inverse?
+    assert_not_predicate has_many_without_inverse_ref, :has_inverse?
 
     belongs_to_without_inverse_ref = Sponsor.reflect_on_association(:sponsor_club)
-    assert !belongs_to_without_inverse_ref.has_inverse?
+    assert_not_predicate belongs_to_without_inverse_ref, :has_inverse?
   end
 
   def test_inverse_of_method_should_supply_the_actual_reflection_instance_it_is_the_inverse_of
@@ -464,7 +464,7 @@ class InverseHasManyTests < ActiveRecord::TestCase
     interest = Interest.create!(man: man)
 
     man.interests.find(interest.id)
-    assert_not man.interests.loaded?
+    assert_not_predicate man.interests, :loaded?
   end
 
   def test_raise_record_not_found_error_when_invalid_ids_are_passed
@@ -504,16 +504,16 @@ class InverseHasManyTests < ActiveRecord::TestCase
     i.man.name = "Charles"
     assert_equal i.man.name, man.name
 
-    assert !man.persisted?
+    assert_not_predicate man, :persisted?
   end
 
   def test_inverse_instance_should_be_set_before_find_callbacks_are_run
     reset_callbacks(Interest, :find) do
       Interest.after_find { raise unless association(:man).loaded? && man.present? }
 
-      assert Man.first.interests.reload.any?
-      assert Man.includes(:interests).first.interests.any?
-      assert Man.joins(:interests).includes(:interests).first.interests.any?
+      assert_predicate Man.first.interests.reload, :any?
+      assert_predicate Man.includes(:interests).first.interests, :any?
+      assert_predicate Man.joins(:interests).includes(:interests).first.interests, :any?
     end
   end
 
@@ -521,9 +521,9 @@ class InverseHasManyTests < ActiveRecord::TestCase
     reset_callbacks(Interest, :initialize) do
       Interest.after_initialize { raise unless association(:man).loaded? && man.present? }
 
-      assert Man.first.interests.reload.any?
-      assert Man.includes(:interests).first.interests.any?
-      assert Man.joins(:interests).includes(:interests).first.interests.any?
+      assert_predicate Man.first.interests.reload, :any?
+      assert_predicate Man.includes(:interests).first.interests, :any?
+      assert_predicate Man.joins(:interests).includes(:interests).first.interests, :any?
     end
   end
 
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index 5d83c9435b..f19a9f5f7a 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -44,11 +44,11 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
 
   def test_has_many_distinct_through_count
     author = authors(:mary)
-    assert !authors(:mary).unique_categorized_posts.loaded?
+    assert_not_predicate authors(:mary).unique_categorized_posts, :loaded?
     assert_queries(1) { assert_equal 1, author.unique_categorized_posts.count }
     assert_queries(1) { assert_equal 1, author.unique_categorized_posts.count(:title) }
     assert_queries(1) { assert_equal 0, author.unique_categorized_posts.where(title: nil).count(:title) }
-    assert !authors(:mary).unique_categorized_posts.loaded?
+    assert_not_predicate authors(:mary).unique_categorized_posts, :loaded?
   end
 
   def test_has_many_distinct_through_find
@@ -454,8 +454,8 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
 
   def test_has_many_through_uses_conditions_specified_on_the_has_many_association
     author = Author.first
-    assert author.comments.present?
-    assert author.nonexistent_comments.blank?
+    assert_predicate author.comments, :present?
+    assert_predicate author.nonexistent_comments, :blank?
   end
 
   def test_has_many_through_uses_correct_attributes
@@ -468,26 +468,26 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
 
     saved_post.tags << new_tag
     assert new_tag.persisted? # consistent with habtm!
-    assert saved_post.persisted?
+    assert_predicate saved_post, :persisted?
     assert_includes saved_post.tags, new_tag
 
-    assert new_tag.persisted?
+    assert_predicate new_tag, :persisted?
     assert_includes saved_post.reload.tags.reload, new_tag
 
     new_post = Post.new(title: "Association replacement works!", body: "You best believe it.")
     saved_tag = tags(:general)
 
     new_post.tags << saved_tag
-    assert !new_post.persisted?
-    assert saved_tag.persisted?
+    assert_not_predicate new_post, :persisted?
+    assert_predicate saved_tag, :persisted?
     assert_includes new_post.tags, saved_tag
 
     new_post.save!
-    assert new_post.persisted?
+    assert_predicate new_post, :persisted?
     assert_includes new_post.reload.tags.reload, saved_tag
 
-    assert !posts(:thinking).tags.build.persisted?
-    assert !posts(:thinking).tags.new.persisted?
+    assert_not_predicate posts(:thinking).tags.build, :persisted?
+    assert_not_predicate posts(:thinking).tags.new, :persisted?
   end
 
   def test_create_associate_when_adding_to_has_many_through
@@ -529,14 +529,14 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
   def test_has_many_through_collection_size_doesnt_load_target_if_not_loaded
     author = authors(:david)
     assert_equal 10, author.comments.size
-    assert !author.comments.loaded?
+    assert_not_predicate author.comments, :loaded?
   end
 
   def test_has_many_through_collection_size_uses_counter_cache_if_it_exists
     c = categories(:general)
     c.categorizations_count = 100
     assert_equal 100, c.categorizations.size
-    assert !c.categorizations.loaded?
+    assert_not_predicate c.categorizations, :loaded?
   end
 
   def test_adding_junk_to_has_many_through_should_raise_type_mismatch
@@ -710,7 +710,7 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     category = david.categories.first
 
     assert_no_queries do
-      assert david.categories.loaded?
+      assert_predicate david.categories, :loaded?
       assert_includes david.categories, category
     end
   end
@@ -720,18 +720,18 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
     category = david.categories.first
 
     david.reload
-    assert ! david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
     assert_queries(1) do
       assert_includes david.categories, category
     end
-    assert ! david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
   end
 
   def test_has_many_through_include_returns_false_for_non_matching_record_to_verify_scoping
     david = authors(:david)
     category = Category.create!(name: "Not Associated")
 
-    assert ! david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
     assert ! david.categories.include?(category)
   end
 
diff --git a/activerecord/test/cases/associations/left_outer_join_association_test.rb b/activerecord/test/cases/associations/left_outer_join_association_test.rb
index c95d0425cd..7b5c394177 100644
--- a/activerecord/test/cases/associations/left_outer_join_association_test.rb
+++ b/activerecord/test/cases/associations/left_outer_join_association_test.rb
@@ -69,15 +69,15 @@ class LeftOuterJoinAssociationTest < ActiveRecord::TestCase
     scope = Post.left_outer_joins(:special_comments).where(id: posts(:sti_comments).id)
 
     # The join should match SpecialComment and its subclasses only
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
-    assert !scope.where("comments.type" => "SubSpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
+    assert_not_empty scope.where("comments.type" => "SubSpecialComment")
   end
 
   def test_does_not_override_select
     authors = Author.select("authors.name, #{%{(authors.author_address_id || ' ' || authors.author_address_extra_id) as addr_id}}").left_outer_joins(:posts)
-    assert authors.any?
-    assert authors.first.respond_to?(:addr_id)
+    assert_predicate authors, :any?
+    assert_respond_to authors.first, :addr_id
   end
 
   test "the default scope of the target is applied when joining associations" do
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index 65d30d011b..03ed1c1d47 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -78,7 +78,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # This ensures that the polymorphism of taggings is being observed correctly
     authors = Author.joins(:tags).where("taggings.taggable_type" => "FakeModel")
-    assert authors.empty?
+    assert_empty authors
   end
 
   # has_many through
@@ -177,7 +177,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     members = Member.joins(:organization_member_details).
                      where("member_details.id" => 9)
-    assert members.empty?
+    assert_empty members
   end
 
   # has_many through
@@ -209,7 +209,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     members = Member.joins(:organization_member_details_2).
                      where("member_details.id" => 9)
-    assert members.empty?
+    assert_empty members
   end
 
   # has_many through
@@ -425,9 +425,9 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # Check the polymorphism of taggings is being observed correctly (in both joins)
     authors = Author.joins(:similar_posts).where("taggings.taggable_type" => "FakeModel")
-    assert authors.empty?
+    assert_empty authors
     authors = Author.joins(:similar_posts).where("taggings_authors_join.taggable_type" => "FakeModel")
-    assert authors.empty?
+    assert_empty authors
   end
 
   def test_nested_has_many_through_with_scope_on_polymorphic_reflection
@@ -456,9 +456,9 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # Ensure STI is respected in the join
     scope = Post.joins(:special_comments_ratings).where(id: posts(:sti_comments).id)
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
-    assert !scope.where("comments.type" => "SubSpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
+    assert_not_empty scope.where("comments.type" => "SubSpecialComment")
   end
 
   def test_has_many_through_with_sti_on_nested_through_reflection
@@ -466,8 +466,8 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     assert_equal [taggings(:special_comment_rating)], taggings
 
     scope = Post.joins(:special_comments_ratings_taggings).where(id: posts(:sti_comments).id)
-    assert scope.where("comments.type" => "Comment").empty?
-    assert !scope.where("comments.type" => "SpecialComment").empty?
+    assert_empty scope.where("comments.type" => "Comment")
+    assert_not_empty scope.where("comments.type" => "SpecialComment")
   end
 
   def test_nested_has_many_through_writers_should_raise_error
@@ -517,7 +517,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
   end
 
   def test_nested_has_many_through_with_conditions_on_through_associations_preload
-    assert Author.where("tags.id" => 100).joins(:misc_post_first_blue_tags).empty?
+    assert_empty Author.where("tags.id" => 100).joins(:misc_post_first_blue_tags)
 
     authors = assert_queries(3) { Author.includes(:misc_post_first_blue_tags).to_a.sort_by(&:id) }
     blue = tags(:blue)
@@ -574,9 +574,9 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
     c = Categorization.new
     c.author = authors(:david)
     c.post_taggings.to_a
-    assert !c.post_taggings.empty?
+    assert_not_empty c.post_taggings
     c.save
-    assert !c.post_taggings.empty?
+    assert_not_empty c.post_taggings
   end
 
   def test_polymorphic_has_many_through_when_through_association_has_not_loaded
diff --git a/activerecord/test/cases/associations_test.rb b/activerecord/test/cases/associations_test.rb
index de04221ea6..fce2a7eed1 100644
--- a/activerecord/test/cases/associations_test.rb
+++ b/activerecord/test/cases/associations_test.rb
@@ -47,7 +47,7 @@ class AssociationsTest < ActiveRecord::TestCase
     ship = Ship.create!(name: "The good ship Dollypop")
     part = ship.parts.create!(name: "Mast")
     part.mark_for_destruction
-    assert ship.parts[0].marked_for_destruction?
+    assert_predicate ship.parts[0], :marked_for_destruction?
   end
 
   def test_loading_the_association_target_should_load_most_recent_attributes_for_child_records_marked_for_destruction
@@ -119,7 +119,7 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
 
     david.posts << (post = Post.new(title: "New on Edge", body: "More cool stuff!"))
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
     assert_includes david.posts, post
   end
 
@@ -127,7 +127,7 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
 
     david.categories << categories(:technology)
-    assert !david.categories.loaded?
+    assert_not_predicate david.categories, :loaded?
     assert_includes david.categories, categories(:technology)
   end
 
@@ -135,23 +135,23 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
 
     david.posts << (post = Post.new(title: "New on Edge", body: "More cool stuff!"))
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
     david.save
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
     assert_includes david.posts, post
   end
 
   def test_push_does_not_lose_additions_to_new_record
     josh = Author.new(name: "Josh")
     josh.posts << Post.new(title: "New on Edge", body: "More cool stuff!")
-    assert josh.posts.loaded?
+    assert_predicate josh.posts, :loaded?
     assert_equal 1, josh.posts.size
   end
 
   def test_append_behaves_like_push
     josh = Author.new(name: "Josh")
     josh.posts.append Post.new(title: "New on Edge", body: "More cool stuff!")
-    assert josh.posts.loaded?
+    assert_predicate josh.posts, :loaded?
     assert_equal 1, josh.posts.size
   end
 
@@ -163,22 +163,22 @@ class AssociationProxyTest < ActiveRecord::TestCase
   def test_save_on_parent_does_not_load_target
     david = developers(:david)
 
-    assert !david.projects.loaded?
+    assert_not_predicate david.projects, :loaded?
     david.update_columns(created_at: Time.now)
-    assert !david.projects.loaded?
+    assert_not_predicate david.projects, :loaded?
   end
 
   def test_load_does_load_target
     david = developers(:david)
 
-    assert !david.projects.loaded?
+    assert_not_predicate david.projects, :loaded?
     david.projects.load
-    assert david.projects.loaded?
+    assert_predicate david.projects, :loaded?
   end
 
   def test_inspect_does_not_reload_a_not_yet_loaded_target
     andreas = Developer.new name: "Andreas", log: "new developer added"
-    assert !andreas.audit_logs.loaded?
+    assert_not_predicate andreas.audit_logs, :loaded?
     assert_match(/message: "new developer added"/, andreas.audit_logs.inspect)
   end
 
@@ -248,14 +248,14 @@ class AssociationProxyTest < ActiveRecord::TestCase
   test "first! works on loaded associations" do
     david = authors(:david)
     assert_equal david.first_posts.first, david.first_posts.reload.first!
-    assert david.first_posts.loaded?
+    assert_predicate david.first_posts, :loaded?
     assert_no_queries { david.first_posts.first! }
   end
 
   def test_pluck_uses_loaded_target
     david = authors(:david)
     assert_equal david.first_posts.pluck(:title), david.first_posts.load.pluck(:title)
-    assert david.first_posts.loaded?
+    assert_predicate david.first_posts, :loaded?
     assert_no_queries { david.first_posts.pluck(:title) }
   end
 
@@ -263,9 +263,9 @@ class AssociationProxyTest < ActiveRecord::TestCase
     david = authors(:david)
     david.posts.reload
 
-    assert david.posts.loaded?
+    assert_predicate david.posts, :loaded?
     david.posts.reset
-    assert !david.posts.loaded?
+    assert_not_predicate david.posts, :loaded?
   end
 end
 
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index c48f7d3518..dc6638d45d 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -99,8 +99,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   end
 
   test "boolean attributes" do
-    assert !Topic.find(1).approved?
-    assert Topic.find(2).approved?
+    assert_not_predicate Topic.find(1), :approved?
+    assert_predicate Topic.find(2), :approved?
   end
 
   test "set attributes" do
@@ -142,16 +142,16 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     assert_respond_to topic, :title=
     assert_respond_to topic, "author_name"
     assert_respond_to topic, "attribute_names"
-    assert !topic.respond_to?("nothingness")
-    assert !topic.respond_to?(:nothingness)
+    assert_not_respond_to topic, "nothingness"
+    assert_not_respond_to topic, :nothingness
   end
 
   test "respond_to? with a custom primary key" do
     keyboard = Keyboard.create
     assert_not_nil keyboard.key_number
     assert_equal keyboard.key_number, keyboard.id
-    assert keyboard.respond_to?("key_number")
-    assert keyboard.respond_to?("id")
+    assert_respond_to keyboard, "key_number"
+    assert_respond_to keyboard, "id"
   end
 
   test "id_before_type_cast with a custom primary key" do
@@ -170,8 +170,8 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     end
 
     topic = klass.allocate
-    assert !topic.respond_to?("nothingness")
-    assert !topic.respond_to?(:nothingness)
+    assert_not_respond_to topic, "nothingness"
+    assert_not_respond_to topic, :nothingness
     assert_respond_to topic, "title"
     assert_respond_to topic, :title
   end
@@ -457,30 +457,30 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     SQL
 
     assert_equal "Firm", object.string_value
-    assert object.string_value?
+    assert_predicate object, :string_value?
 
     object.string_value = "  "
-    assert !object.string_value?
+    assert_not_predicate object, :string_value?
 
     assert_equal 1, object.int_value.to_i
-    assert object.int_value?
+    assert_predicate object, :int_value?
 
     object.int_value = "0"
-    assert !object.int_value?
+    assert_not_predicate object, :int_value?
   end
 
   test "non-attribute read and write" do
     topic = Topic.new
-    assert !topic.respond_to?("mumbo")
+    assert_not_respond_to topic, "mumbo"
     assert_raise(NoMethodError) { topic.mumbo }
     assert_raise(NoMethodError) { topic.mumbo = 5 }
   end
 
   test "undeclared attribute method does not affect respond_to? and method_missing" do
     topic = @target.new(title: "Budget")
-    assert topic.respond_to?("title")
+    assert_respond_to topic, "title"
     assert_equal "Budget", topic.title
-    assert !topic.respond_to?("title_hello_world")
+    assert_not_respond_to topic, "title_hello_world"
     assert_raise(NoMethodError) { topic.title_hello_world }
   end
 
@@ -491,7 +491,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       @target.attribute_method_prefix prefix
 
       meth = "#{prefix}title"
-      assert topic.respond_to?(meth)
+      assert_respond_to topic, meth
       assert_equal ["title"], topic.send(meth)
       assert_equal ["title", "a"], topic.send(meth, "a")
       assert_equal ["title", 1, 2, 3], topic.send(meth, 1, 2, 3)
@@ -505,7 +505,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       topic = @target.new(title: "Budget")
 
       meth = "title#{suffix}"
-      assert topic.respond_to?(meth)
+      assert_respond_to topic, meth
       assert_equal ["title"], topic.send(meth)
       assert_equal ["title", "a"], topic.send(meth, "a")
       assert_equal ["title", 1, 2, 3], topic.send(meth, 1, 2, 3)
@@ -519,7 +519,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
       topic = @target.new(title: "Budget")
 
       meth = "#{prefix}title#{suffix}"
-      assert topic.respond_to?(meth)
+      assert_respond_to topic, meth
       assert_equal ["title"], topic.send(meth)
       assert_equal ["title", "a"], topic.send(meth, "a")
       assert_equal ["title", 1, 2, 3], topic.send(meth, 1, 2, 3)
@@ -541,7 +541,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     else
       topic = Topic.all.merge!(select: "topics.*, 1=2 as is_test").first
     end
-    assert !topic.is_test?
+    assert_not_predicate topic, :is_test?
   end
 
   test "typecast attribute from select to true" do
@@ -552,7 +552,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     else
       topic = Topic.all.merge!(select: "topics.*, 2=2 as is_test").first
     end
-    assert topic.is_test?
+    assert_predicate topic, :is_test?
   end
 
   test "raises ActiveRecord::DangerousAttributeError when defining an AR method in a model" do
@@ -743,7 +743,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
         expected_time = Time.utc(2000, 01, 01, 10)
 
         assert_equal expected_time, record.bonus_time
-        assert record.bonus_time.utc?
+        assert_predicate record.bonus_time, :utc?
       end
     end
   end
@@ -767,7 +767,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     privatize("title")
 
     topic = @target.new(title: "The pros and cons of programming naked.")
-    assert !topic.respond_to?(:title)
+    assert_not_respond_to topic, :title
     exception = assert_raise(NoMethodError) { topic.title }
     assert_includes exception.message, "private method"
     assert_equal "I'm private", topic.send(:title)
@@ -777,7 +777,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     privatize("title=(value)")
 
     topic = @target.new
-    assert !topic.respond_to?(:title=)
+    assert_not_respond_to topic, :title=
     exception = assert_raise(NoMethodError) { topic.title = "Pants" }
     assert_includes exception.message, "private method"
     topic.send(:title=, "Very large pants")
@@ -787,7 +787,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
     privatize("title?")
 
     topic = @target.new(title: "Isaac Newton's pants")
-    assert !topic.respond_to?(:title?)
+    assert_not_respond_to topic, :title?
     exception = assert_raise(NoMethodError) { topic.title? }
     assert_includes exception.message, "private method"
     assert topic.send(:title?)
@@ -979,9 +979,9 @@ class AttributeMethodsTest < ActiveRecord::TestCase
   test "came_from_user?" do
     model = @target.first
 
-    assert_not model.id_came_from_user?
+    assert_not_predicate model, :id_came_from_user?
     model.id = "omg"
-    assert model.id_came_from_user?
+    assert_predicate model, :id_came_from_user?
   end
 
   test "accessed_fields" do
diff --git a/activerecord/test/cases/attributes_test.rb b/activerecord/test/cases/attributes_test.rb
index 8ebfee61ff..3bc56694be 100644
--- a/activerecord/test/cases/attributes_test.rb
+++ b/activerecord/test/cases/attributes_test.rb
@@ -211,7 +211,7 @@ module ActiveRecord
     end
 
     test "attributes not backed by database columns are not dirty when unchanged" do
-      refute OverloadedType.new.non_existent_decimal_changed?
+      assert_not_predicate OverloadedType.new, :non_existent_decimal_changed?
     end
 
     test "attributes not backed by database columns are always initialized" do
@@ -245,13 +245,13 @@ module ActiveRecord
 
       model.foo << "asdf"
       assert_equal "lolasdf", model.foo
-      assert model.foo_changed?
+      assert_predicate model, :foo_changed?
 
       model.reload
       assert_equal "lol", model.foo
 
       model.foo = "lol"
-      refute model.changed?
+      assert_not_predicate model, :changed?
     end
 
     test "attributes not backed by database columns appear in inspect" do
diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 4d8368fd8a..b8243d148a 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -50,8 +50,8 @@ class TestAutosaveAssociationsInGeneral < ActiveRecord::TestCase
     }
 
     u = person.create!(first_name: "cool")
-    u.update_attributes!(first_name: "nah") # still valid because validation only applies on 'create'
-    assert reference.create!(person: u).persisted?
+    u.update!(first_name: "nah") # still valid because validation only applies on 'create'
+    assert_predicate reference.create!(person: u), :persisted?
   end
 
   def test_should_not_add_the_same_callbacks_multiple_times_for_has_one
@@ -74,7 +74,7 @@ class TestAutosaveAssociationsInGeneral < ActiveRecord::TestCase
     ship = ShipWithoutNestedAttributes.new
     ship.prisoners.build
 
-    assert_not ship.valid?
+    assert_not_predicate ship, :valid?
     assert_equal 1, ship.errors[:name].length
   end
 
@@ -99,35 +99,35 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
 
   def test_should_save_parent_but_not_invalid_child
     firm = Firm.new(name: "GlobalMegaCorp")
-    assert firm.valid?
+    assert_predicate firm, :valid?
 
     firm.build_account_using_primary_key
-    assert !firm.build_account_using_primary_key.valid?
+    assert_not_predicate firm.build_account_using_primary_key, :valid?
 
     assert firm.save
-    assert !firm.account_using_primary_key.persisted?
+    assert_not_predicate firm.account_using_primary_key, :persisted?
   end
 
   def test_save_fails_for_invalid_has_one
     firm = Firm.first
-    assert firm.valid?
+    assert_predicate firm, :valid?
 
     firm.build_account
 
-    assert !firm.account.valid?
-    assert !firm.valid?
+    assert_not_predicate firm.account, :valid?
+    assert_not_predicate firm, :valid?
     assert !firm.save
     assert_equal ["is invalid"], firm.errors["account"]
   end
 
   def test_save_succeeds_for_invalid_has_one_with_validate_false
     firm = Firm.first
-    assert firm.valid?
+    assert_predicate firm, :valid?
 
     firm.build_unvalidated_account
 
-    assert !firm.unvalidated_account.valid?
-    assert firm.valid?
+    assert_not_predicate firm.unvalidated_account, :valid?
+    assert_predicate firm, :valid?
     assert firm.save
   end
 
@@ -136,10 +136,10 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
 
     account = firm.build_account("credit_limit" => 1000)
     assert_equal account, firm.account
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     assert firm.save
     assert_equal account, firm.account
-    assert account.persisted?
+    assert_predicate account, :persisted?
   end
 
   def test_build_before_either_saved
@@ -147,16 +147,16 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
 
     firm.account = account = Account.new("credit_limit" => 1000)
     assert_equal account, firm.account
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     assert firm.save
     assert_equal account, firm.account
-    assert account.persisted?
+    assert_predicate account, :persisted?
   end
 
   def test_assignment_before_parent_saved
     firm = Firm.new("name" => "GlobalMegaCorp")
     firm.account = a = Account.find(1)
-    assert !firm.persisted?
+    assert_not_predicate firm, :persisted?
     assert_equal a, firm.account
     assert firm.save
     assert_equal a, firm.account
@@ -167,12 +167,12 @@ class TestDefaultAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCas
   def test_assignment_before_either_saved
     firm = Firm.new("name" => "GlobalMegaCorp")
     firm.account = a = Account.new("credit_limit" => 1000)
-    assert !firm.persisted?
-    assert !a.persisted?
+    assert_not_predicate firm, :persisted?
+    assert_not_predicate a, :persisted?
     assert_equal a, firm.account
     assert firm.save
-    assert firm.persisted?
-    assert a.persisted?
+    assert_predicate firm, :persisted?
+    assert_predicate a, :persisted?
     assert_equal a, firm.account
     firm.association(:account).reload
     assert_equal a, firm.account
@@ -221,13 +221,13 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
 
   def test_should_save_parent_but_not_invalid_child
     client = Client.new(name: "Joe (the Plumber)")
-    assert client.valid?
+    assert_predicate client, :valid?
 
     client.build_firm
-    assert !client.firm.valid?
+    assert_not_predicate client.firm, :valid?
 
     assert client.save
-    assert !client.firm.persisted?
+    assert_not_predicate client.firm, :persisted?
   end
 
   def test_save_fails_for_invalid_belongs_to
@@ -235,8 +235,8 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     assert log = AuditLog.create(developer_id: 0, message: " ")
 
     log.developer = Developer.new
-    assert !log.developer.valid?
-    assert !log.valid?
+    assert_not_predicate log.developer, :valid?
+    assert_not_predicate log, :valid?
     assert !log.save
     assert_equal ["is invalid"], log.errors["developer"]
   end
@@ -246,8 +246,8 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     assert log = AuditLog.create(developer_id: 0, message: " ")
 
     log.unvalidated_developer = Developer.new
-    assert !log.unvalidated_developer.valid?
-    assert log.valid?
+    assert_not_predicate log.unvalidated_developer, :valid?
+    assert_predicate log, :valid?
     assert log.save
   end
 
@@ -256,10 +256,10 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     apple = Firm.new("name" => "Apple")
     client.firm = apple
     assert_equal apple, client.firm
-    assert !apple.persisted?
+    assert_not_predicate apple, :persisted?
     assert client.save
     assert apple.save
-    assert apple.persisted?
+    assert_predicate apple, :persisted?
     assert_equal apple, client.firm
     client.association(:firm).reload
     assert_equal apple, client.firm
@@ -269,11 +269,11 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     final_cut = Client.new("name" => "Final Cut")
     apple = Firm.new("name" => "Apple")
     final_cut.firm = apple
-    assert !final_cut.persisted?
-    assert !apple.persisted?
+    assert_not_predicate final_cut, :persisted?
+    assert_not_predicate apple, :persisted?
     assert final_cut.save
-    assert final_cut.persisted?
-    assert apple.persisted?
+    assert_predicate final_cut, :persisted?
+    assert_predicate apple, :persisted?
     assert_equal apple, final_cut.firm
     final_cut.association(:firm).reload
     assert_equal apple, final_cut.firm
@@ -382,7 +382,7 @@ class TestDefaultAutosaveAssociationOnABelongsToAssociation < ActiveRecord::Test
     auditlog.developer    = invalid_developer
     auditlog.developer_id = valid_developer.id
 
-    assert auditlog.valid?
+    assert_predicate auditlog, :valid?
   end
 end
 
@@ -395,8 +395,8 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
     molecule.electrons = [valid_electron, invalid_electron]
     molecule.save
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
     assert_not molecule.persisted?, "Molecule should not be persisted when its electrons are invalid"
   end
 
@@ -408,9 +408,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     guitar.tuning_pegs = [tuning_peg_valid, tuning_peg_invalid]
 
-    assert_not tuning_peg_invalid.valid?
-    assert tuning_peg_valid.valid?
-    assert_not guitar.valid?
+    assert_not_predicate tuning_peg_invalid, :valid?
+    assert_predicate tuning_peg_valid, :valid?
+    assert_not_predicate guitar, :valid?
     assert_equal ["is not a number"], guitar.errors["tuning_pegs[1].pitch"]
     assert_not_equal ["is not a number"], guitar.errors["tuning_pegs.pitch"]
   end
@@ -425,9 +425,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     molecule.electrons = [valid_electron, invalid_electron]
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
-    assert_not molecule.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
+    assert_not_predicate molecule, :valid?
     assert_equal ["can't be blank"], molecule.errors["electrons[1].name"]
     assert_not_equal ["can't be blank"], molecule.errors["electrons.name"]
   ensure
@@ -441,9 +441,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     molecule.electrons = [valid_electron, invalid_electron]
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
-    assert_not molecule.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
+    assert_not_predicate molecule, :valid?
     assert_equal [{ error: :blank }], molecule.errors.details[:"electrons.name"]
   end
 
@@ -455,9 +455,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     guitar.tuning_pegs = [tuning_peg_valid, tuning_peg_invalid]
 
-    assert_not tuning_peg_invalid.valid?
-    assert tuning_peg_valid.valid?
-    assert_not guitar.valid?
+    assert_not_predicate tuning_peg_invalid, :valid?
+    assert_predicate tuning_peg_valid, :valid?
+    assert_not_predicate guitar, :valid?
     assert_equal [{ error: :not_a_number, value: nil }], guitar.errors.details[:"tuning_pegs[1].pitch"]
     assert_equal [], guitar.errors.details[:"tuning_pegs.pitch"]
   end
@@ -472,9 +472,9 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
 
     molecule.electrons = [valid_electron, invalid_electron]
 
-    assert_not invalid_electron.valid?
-    assert valid_electron.valid?
-    assert_not molecule.valid?
+    assert_not_predicate invalid_electron, :valid?
+    assert_predicate valid_electron, :valid?
+    assert_not_predicate molecule, :valid?
     assert_equal [{ error: :blank }], molecule.errors.details[:"electrons[1].name"]
     assert_equal [], molecule.errors.details[:"electrons.name"]
   ensure
@@ -488,8 +488,8 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttrib
     molecule.electrons = [valid_electron]
     molecule.save
 
-    assert valid_electron.valid?
-    assert molecule.persisted?
+    assert_predicate valid_electron, :valid?
+    assert_predicate molecule, :persisted?
     assert_equal 1, molecule.electrons.count
   end
 end
@@ -500,21 +500,21 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
   def test_invalid_adding
     firm = Firm.find(1)
     assert !(firm.clients_of_firm << c = Client.new)
-    assert !c.persisted?
-    assert !firm.valid?
+    assert_not_predicate c, :persisted?
+    assert_not_predicate firm, :valid?
     assert !firm.save
-    assert !c.persisted?
+    assert_not_predicate c, :persisted?
   end
 
   def test_invalid_adding_before_save
     new_firm = Firm.new("name" => "A New Firm, Inc")
     new_firm.clients_of_firm.concat([c = Client.new, Client.new("name" => "Apple")])
-    assert !c.persisted?
-    assert !c.valid?
-    assert !new_firm.valid?
+    assert_not_predicate c, :persisted?
+    assert_not_predicate c, :valid?
+    assert_not_predicate new_firm, :valid?
     assert !new_firm.save
-    assert !c.persisted?
-    assert !new_firm.persisted?
+    assert_not_predicate c, :persisted?
+    assert_not_predicate new_firm, :persisted?
   end
 
   def test_invalid_adding_with_validate_false
@@ -522,10 +522,10 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
     client = Client.new
     firm.unvalidated_clients_of_firm << client
 
-    assert firm.valid?
-    assert !client.valid?
+    assert_predicate firm, :valid?
+    assert_not_predicate client, :valid?
     assert firm.save
-    assert !client.persisted?
+    assert_not_predicate client, :persisted?
   end
 
   def test_valid_adding_with_validate_false
@@ -534,24 +534,24 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
     firm = Firm.first
     client = Client.new("name" => "Apple")
 
-    assert firm.valid?
-    assert client.valid?
-    assert !client.persisted?
+    assert_predicate firm, :valid?
+    assert_predicate client, :valid?
+    assert_not_predicate client, :persisted?
 
     firm.unvalidated_clients_of_firm << client
 
     assert firm.save
-    assert client.persisted?
+    assert_predicate client, :persisted?
     assert_equal no_of_clients + 1, Client.count
   end
 
   def test_invalid_build
     new_client = companies(:first_firm).clients_of_firm.build
-    assert !new_client.persisted?
-    assert !new_client.valid?
+    assert_not_predicate new_client, :persisted?
+    assert_not_predicate new_client, :valid?
     assert_equal new_client, companies(:first_firm).clients_of_firm.last
     assert !companies(:first_firm).save
-    assert !new_client.persisted?
+    assert_not_predicate new_client, :persisted?
     assert_equal 2, companies(:first_firm).clients_of_firm.reload.size
   end
 
@@ -570,8 +570,8 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
     assert_equal no_of_firms, Firm.count      # Firm was not saved to database.
     assert_equal no_of_clients, Client.count  # Clients were not saved to database.
     assert new_firm.save
-    assert new_firm.persisted?
-    assert c.persisted?
+    assert_predicate new_firm, :persisted?
+    assert_predicate c, :persisted?
     assert_equal new_firm, c.firm
     assert_equal no_of_firms + 1, Firm.count      # Firm was saved to database.
     assert_equal no_of_clients + 2, Client.count  # Clients were saved to database.
@@ -601,11 +601,11 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
   def test_build_before_save
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build("name" => "Another Client") }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     company.name += "-changed"
     assert_queries(2) { assert company.save }
-    assert new_client.persisted?
+    assert_predicate new_client, :persisted?
     assert_equal 3, company.clients_of_firm.reload.size
   end
 
@@ -621,11 +621,11 @@ class TestDefaultAutosaveAssociationOnAHasManyAssociation < ActiveRecord::TestCa
   def test_build_via_block_before_save
     company = companies(:first_firm)
     new_client = assert_no_queries(ignore_none: false) { company.clients_of_firm.build { |client| client.name = "Another Client" } }
-    assert !company.clients_of_firm.loaded?
+    assert_not_predicate company.clients_of_firm, :loaded?
 
     company.name += "-changed"
     assert_queries(2) { assert company.save }
-    assert new_client.persisted?
+    assert_predicate new_client, :persisted?
     assert_equal 3, company.clients_of_firm.reload.size
   end
 
@@ -657,62 +657,62 @@ class TestDefaultAutosaveAssociationOnNewRecord < ActiveRecord::TestCase
     new_account = Account.new("credit_limit" => 1000)
     new_firm = Firm.new("name" => "some firm")
 
-    assert !new_firm.persisted?
+    assert_not_predicate new_firm, :persisted?
     new_account.firm = new_firm
     new_account.save!
 
-    assert new_firm.persisted?
+    assert_predicate new_firm, :persisted?
 
     new_account = Account.new("credit_limit" => 1000)
     new_autosaved_firm = Firm.new("name" => "some firm")
 
-    assert !new_autosaved_firm.persisted?
+    assert_not_predicate new_autosaved_firm, :persisted?
     new_account.unautosaved_firm = new_autosaved_firm
     new_account.save!
 
-    assert !new_autosaved_firm.persisted?
+    assert_not_predicate new_autosaved_firm, :persisted?
   end
 
   def test_autosave_new_record_on_has_one_can_be_disabled_per_relationship
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.account = account
     firm.save!
 
-    assert account.persisted?
+    assert_predicate account, :persisted?
 
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
     firm.unautosaved_account = account
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.unautosaved_account = account
     firm.save!
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
   end
 
   def test_autosave_new_record_on_has_many_can_be_disabled_per_relationship
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.accounts << account
 
     firm.save!
-    assert account.persisted?
+    assert_predicate account, :persisted?
 
     firm = Firm.new("name" => "some firm")
     account = Account.new("credit_limit" => 1000)
 
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
     firm.unautosaved_accounts << account
 
     firm.save!
-    assert !account.persisted?
+    assert_not_predicate account, :persisted?
   end
 
   def test_autosave_new_record_with_after_create_callback
@@ -745,18 +745,18 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @pirate.mark_for_destruction
     @pirate.ship.mark_for_destruction
 
-    assert !@pirate.reload.marked_for_destruction?
-    assert !@pirate.ship.reload.marked_for_destruction?
+    assert_not_predicate @pirate.reload, :marked_for_destruction?
+    assert_not_predicate @pirate.ship.reload, :marked_for_destruction?
   end
 
   # has_one
   def test_should_destroy_a_child_association_as_part_of_the_save_transaction_if_it_was_marked_for_destruction
-    assert !@pirate.ship.marked_for_destruction?
+    assert_not_predicate @pirate.ship, :marked_for_destruction?
 
     @pirate.ship.mark_for_destruction
     id = @pirate.ship.id
 
-    assert @pirate.ship.marked_for_destruction?
+    assert_predicate @pirate.ship, :marked_for_destruction?
     assert Ship.find_by_id(id)
 
     @pirate.save
@@ -766,7 +766,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
 
   def test_should_skip_validation_on_a_child_association_if_marked_for_destruction
     @pirate.ship.name = ""
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.ship.mark_for_destruction
     @pirate.ship.expects(:valid?).never
@@ -812,12 +812,12 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
 
   # belongs_to
   def test_should_destroy_a_parent_association_as_part_of_the_save_transaction_if_it_was_marked_for_destruction
-    assert !@ship.pirate.marked_for_destruction?
+    assert_not_predicate @ship.pirate, :marked_for_destruction?
 
     @ship.pirate.mark_for_destruction
     id = @ship.pirate.id
 
-    assert @ship.pirate.marked_for_destruction?
+    assert_predicate @ship.pirate, :marked_for_destruction?
     assert Pirate.find_by_id(id)
 
     @ship.save
@@ -827,7 +827,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
 
   def test_should_skip_validation_on_a_parent_association_if_marked_for_destruction
     @ship.pirate.catchphrase = ""
-    assert !@ship.valid?
+    assert_not_predicate @ship, :valid?
 
     @ship.pirate.mark_for_destruction
     @ship.pirate.expects(:valid?).never
@@ -881,7 +881,7 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     ids.each { |id| assert klass.find_by_id(id) }
 
     @pirate.save
-    assert @pirate.reload.birds.empty?
+    assert_empty @pirate.reload.birds
     ids.each { |id| assert_nil klass.find_by_id(id) }
   end
 
@@ -889,14 +889,14 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @pirate.birds.create!(name: :parrot)
     @pirate.birds.first.destroy
     @pirate.save!
-    assert @pirate.reload.birds.empty?
+    assert_empty @pirate.reload.birds
   end
 
   def test_should_skip_validation_on_has_many_if_marked_for_destruction
     2.times { |i| @pirate.birds.create!(name: "birds_#{i}") }
 
     @pirate.birds.each { |bird| bird.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.birds.each do |bird|
       bird.mark_for_destruction
@@ -909,10 +909,10 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     @pirate.birds.create!(name: "birds_1")
 
     @pirate.birds.each { |bird| bird.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.birds.each(&:destroy)
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 
   def test_a_child_marked_for_destruction_should_not_be_destroyed_twice_while_saving_has_many
@@ -1010,17 +1010,17 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
       @pirate.save
     end
 
-    assert @pirate.reload.parrots.empty?
+    assert_empty @pirate.reload.parrots
 
     join_records = Pirate.connection.select_all("SELECT * FROM parrots_pirates WHERE pirate_id = #{@pirate.id}")
-    assert join_records.empty?
+    assert_empty join_records
   end
 
   def test_should_skip_validation_on_habtm_if_marked_for_destruction
     2.times { |i| @pirate.parrots.create!(name: "parrots_#{i}") }
 
     @pirate.parrots.each { |parrot| parrot.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.parrots.each do |parrot|
       parrot.mark_for_destruction
@@ -1028,17 +1028,17 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
     end
 
     @pirate.save!
-    assert @pirate.reload.parrots.empty?
+    assert_empty @pirate.reload.parrots
   end
 
   def test_should_skip_validation_on_habtm_if_destroyed
     @pirate.parrots.create!(name: "parrots_1")
 
     @pirate.parrots.each { |parrot| parrot.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
 
     @pirate.parrots.each(&:destroy)
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 
   def test_a_child_marked_for_destruction_should_not_be_destroyed_twice_while_saving_habtm
@@ -1145,16 +1145,16 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
 
   def test_should_automatically_validate_the_associated_model
     @pirate.ship.name = ""
-    assert @pirate.invalid?
-    assert @pirate.errors[:"ship.name"].any?
+    assert_predicate @pirate, :invalid?
+    assert_predicate @pirate.errors[:"ship.name"], :any?
   end
 
   def test_should_merge_errors_on_the_associated_models_onto_the_parent_even_if_it_is_not_valid
     @pirate.ship.name   = nil
     @pirate.catchphrase = nil
-    assert @pirate.invalid?
-    assert @pirate.errors[:"ship.name"].any?
-    assert @pirate.errors[:catchphrase].any?
+    assert_predicate @pirate, :invalid?
+    assert_predicate @pirate.errors[:"ship.name"], :any?
+    assert_predicate @pirate.errors[:catchphrase], :any?
   end
 
   def test_should_not_ignore_different_error_messages_on_the_same_attribute
@@ -1163,7 +1163,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
     Ship.validates_format_of :name, with: /\w/
     @pirate.ship.name   = ""
     @pirate.catchphrase = nil
-    assert @pirate.invalid?
+    assert_predicate @pirate, :invalid?
     assert_equal ["can't be blank", "is invalid"], @pirate.errors[:"ship.name"]
   ensure
     Ship._validators = old_validators if old_validators
@@ -1244,7 +1244,7 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
     ship = ShipWithoutNestedAttributes.new(name: "The Black Flag")
     ship.parts.build.mark_for_destruction
 
-    assert_not ship.valid?
+    assert_not_predicate ship, :valid?
   end
 end
 
@@ -1299,16 +1299,16 @@ class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
 
   def test_should_automatically_validate_the_associated_model
     @ship.pirate.catchphrase = ""
-    assert @ship.invalid?
-    assert @ship.errors[:"pirate.catchphrase"].any?
+    assert_predicate @ship, :invalid?
+    assert_predicate @ship.errors[:"pirate.catchphrase"], :any?
   end
 
   def test_should_merge_errors_on_the_associated_model_onto_the_parent_even_if_it_is_not_valid
     @ship.name = nil
     @ship.pirate.catchphrase = nil
-    assert @ship.invalid?
-    assert @ship.errors[:name].any?
-    assert @ship.errors[:"pirate.catchphrase"].any?
+    assert_predicate @ship, :invalid?
+    assert_predicate @ship.errors[:name], :any?
+    assert_predicate @ship.errors[:"pirate.catchphrase"], :any?
   end
 
   def test_should_still_allow_to_bypass_validations_on_the_associated_model
@@ -1403,17 +1403,17 @@ module AutosaveAssociationOnACollectionAssociationTests
   def test_should_automatically_validate_the_associated_models
     @pirate.send(@association_name).each { |child| child.name = "" }
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["can't be blank"], @pirate.errors["#{@association_name}.name"]
-    assert @pirate.errors[@association_name].empty?
+    assert_empty @pirate.errors[@association_name]
   end
 
   def test_should_not_use_default_invalid_error_on_associated_models
     @pirate.send(@association_name).build(name: "")
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["can't be blank"], @pirate.errors["#{@association_name}.name"]
-    assert @pirate.errors[@association_name].empty?
+    assert_empty @pirate.errors[@association_name]
   end
 
   def test_should_default_invalid_error_from_i18n
@@ -1423,10 +1423,10 @@ module AutosaveAssociationOnACollectionAssociationTests
 
     @pirate.send(@association_name).build(name: "")
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["cannot be blank"], @pirate.errors["#{@association_name}.name"]
     assert_equal ["#{@association_name.to_s.humanize} name cannot be blank"], @pirate.errors.full_messages
-    assert @pirate.errors[@association_name].empty?
+    assert_empty @pirate.errors[@association_name]
   ensure
     I18n.backend = I18n::Backend::Simple.new
   end
@@ -1435,9 +1435,9 @@ module AutosaveAssociationOnACollectionAssociationTests
     @pirate.send(@association_name).each { |child| child.name = "" }
     @pirate.catchphrase = nil
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
     assert_equal ["can't be blank"], @pirate.errors["#{@association_name}.name"]
-    assert @pirate.errors[:catchphrase].any?
+    assert_predicate @pirate.errors[:catchphrase], :any?
   end
 
   def test_should_allow_to_bypass_validations_on_the_associated_models_on_update
@@ -1595,10 +1595,10 @@ class TestAutosaveAssociationValidationsOnAHasManyAssociation < ActiveRecord::Te
   end
 
   test "should automatically validate associations" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.birds.each { |bird| bird.name = "" }
 
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 end
 
@@ -1613,15 +1613,15 @@ class TestAutosaveAssociationValidationsOnAHasOneAssociation < ActiveRecord::Tes
   end
 
   test "should automatically validate associations with :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.ship.name = ""
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 
   test "should not automatically add validate associations without :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.non_validated_ship.name = ""
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 end
 
@@ -1634,15 +1634,15 @@ class TestAutosaveAssociationValidationsOnABelongsToAssociation < ActiveRecord::
   end
 
   test "should automatically validate associations with :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.parrot = Parrot.new(name: "")
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 
   test "should not automatically validate associations without :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.non_validated_parrot = Parrot.new(name: "")
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 end
 
@@ -1655,17 +1655,17 @@ class TestAutosaveAssociationValidationsOnAHABTMAssociation < ActiveRecord::Test
   end
 
   test "should automatically validate associations with :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.parrots = [ Parrot.new(name: "popuga") ]
     @pirate.parrots.each { |parrot| parrot.name = "" }
-    assert !@pirate.valid?
+    assert_not_predicate @pirate, :valid?
   end
 
   test "should not automatically validate associations without :validate => true" do
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
     @pirate.non_validated_parrots = [ Parrot.new(name: "popuga") ]
     @pirate.non_validated_parrots.each { |parrot| parrot.name = "" }
-    assert @pirate.valid?
+    assert_predicate @pirate, :valid?
   end
 end
 
@@ -1686,7 +1686,7 @@ class TestAutosaveAssociationValidationMethodsGeneration < ActiveRecord::TestCas
   end
 
   test "should not generate validation methods for has_one associations without :validate => true" do
-    assert !@pirate.respond_to?(:validate_associated_records_for_non_validated_ship)
+    assert_not_respond_to @pirate, :validate_associated_records_for_non_validated_ship
   end
 
   test "should generate validation methods for belongs_to associations with :validate => true" do
@@ -1694,7 +1694,7 @@ class TestAutosaveAssociationValidationMethodsGeneration < ActiveRecord::TestCas
   end
 
   test "should not generate validation methods for belongs_to associations without :validate => true" do
-    assert !@pirate.respond_to?(:validate_associated_records_for_non_validated_parrot)
+    assert_not_respond_to @pirate, :validate_associated_records_for_non_validated_parrot
   end
 
   test "should generate validation methods for HABTM associations with :validate => true" do
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index a49990008c..7dfb05a6a5 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -147,8 +147,8 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   def test_table_exists
-    assert !NonExistentTable.table_exists?
-    assert Topic.table_exists?
+    assert_not_predicate NonExistentTable, :table_exists?
+    assert_predicate Topic, :table_exists?
   end
 
   def test_preserving_date_objects
@@ -450,7 +450,7 @@ class BasicsTest < ActiveRecord::TestCase
 
   def test_default_values
     topic = Topic.new
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_nil topic.written_on
     assert_nil topic.bonus_time
     assert_nil topic.last_read
@@ -458,7 +458,7 @@ class BasicsTest < ActiveRecord::TestCase
     topic.save
 
     topic = Topic.find(topic.id)
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_nil topic.last_read
 
     # Oracle has some funky default handling, so it requires a bit of
@@ -727,9 +727,9 @@ class BasicsTest < ActiveRecord::TestCase
     b_nil = Boolean.find(nil_id)
     assert_nil b_nil.value
     b_false = Boolean.find(false_id)
-    assert !b_false.value?
+    assert_not_predicate b_false, :value?
     b_true = Boolean.find(true_id)
-    assert b_true.value?
+    assert_predicate b_true, :value?
   end
 
   def test_boolean_without_questionmark
@@ -753,9 +753,9 @@ class BasicsTest < ActiveRecord::TestCase
     b_blank = Boolean.find(blank_id)
     assert_nil b_blank.value
     b_false = Boolean.find(false_id)
-    assert !b_false.value?
+    assert_not_predicate b_false, :value?
     b_true = Boolean.find(true_id)
-    assert b_true.value?
+    assert_predicate b_true, :value?
   end
 
   def test_new_record_returns_boolean
@@ -768,7 +768,7 @@ class BasicsTest < ActiveRecord::TestCase
     duped_topic = nil
     assert_nothing_raised { duped_topic = topic.dup }
     assert_equal topic.title, duped_topic.title
-    assert !duped_topic.persisted?
+    assert_not_predicate duped_topic, :persisted?
 
     # test if the attributes have been duped
     topic.title = "a"
@@ -786,7 +786,7 @@ class BasicsTest < ActiveRecord::TestCase
 
     # test if saved clone object differs from original
     duped_topic.save
-    assert duped_topic.persisted?
+    assert_predicate duped_topic, :persisted?
     assert_not_equal duped_topic.id, topic.id
 
     duped_topic.reload
@@ -807,7 +807,7 @@ class BasicsTest < ActiveRecord::TestCase
     assert_nothing_raised { dup = dev.dup }
     assert_kind_of DeveloperSalary, dup.salary
     assert_equal dev.salary.amount, dup.salary.amount
-    assert !dup.persisted?
+    assert_not_predicate dup, :persisted?
 
     # test if the attributes have been duped
     original_amount = dup.salary.amount
@@ -815,7 +815,7 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal original_amount, dup.salary.amount
 
     assert dup.save
-    assert dup.persisted?
+    assert_predicate dup, :persisted?
     assert_not_equal dup.id, dev.id
   end
 
@@ -835,22 +835,22 @@ class BasicsTest < ActiveRecord::TestCase
 
   def test_clone_of_new_object_with_defaults
     developer = Developer.new
-    assert !developer.name_changed?
-    assert !developer.salary_changed?
+    assert_not_predicate developer, :name_changed?
+    assert_not_predicate developer, :salary_changed?
 
     cloned_developer = developer.clone
-    assert !cloned_developer.name_changed?
-    assert !cloned_developer.salary_changed?
+    assert_not_predicate cloned_developer, :name_changed?
+    assert_not_predicate cloned_developer, :salary_changed?
   end
 
   def test_clone_of_new_object_marks_attributes_as_dirty
     developer = Developer.new name: "Bjorn", salary: 100000
-    assert developer.name_changed?
-    assert developer.salary_changed?
+    assert_predicate developer, :name_changed?
+    assert_predicate developer, :salary_changed?
 
     cloned_developer = developer.clone
-    assert cloned_developer.name_changed?
-    assert cloned_developer.salary_changed?
+    assert_predicate cloned_developer, :name_changed?
+    assert_predicate cloned_developer, :salary_changed?
   end
 
   def test_clone_of_new_object_marks_as_dirty_only_changed_attributes
@@ -859,24 +859,24 @@ class BasicsTest < ActiveRecord::TestCase
     assert !developer.salary_changed?         # attribute has non-nil default value, so treated as not changed
 
     cloned_developer = developer.clone
-    assert cloned_developer.name_changed?
+    assert_predicate cloned_developer, :name_changed?
     assert !cloned_developer.salary_changed?  # ... and cloned instance should behave same
   end
 
   def test_dup_of_saved_object_marks_attributes_as_dirty
     developer = Developer.create! name: "Bjorn", salary: 100000
-    assert !developer.name_changed?
-    assert !developer.salary_changed?
+    assert_not_predicate developer, :name_changed?
+    assert_not_predicate developer, :salary_changed?
 
     cloned_developer = developer.dup
     assert cloned_developer.name_changed?     # both attributes differ from defaults
-    assert cloned_developer.salary_changed?
+    assert_predicate cloned_developer, :salary_changed?
   end
 
   def test_dup_of_saved_object_marks_as_dirty_only_changed_attributes
     developer = Developer.create! name: "Bjorn"
     assert !developer.name_changed?           # both attributes of saved object should be treated as not changed
-    assert !developer.salary_changed?
+    assert_not_predicate developer, :salary_changed?
 
     cloned_developer = developer.dup
     assert cloned_developer.name_changed?     # ... but on cloned object should be
@@ -951,14 +951,14 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   def test_toggle_attribute
-    assert !topics(:first).approved?
+    assert_not_predicate topics(:first), :approved?
     topics(:first).toggle!(:approved)
-    assert topics(:first).approved?
+    assert_predicate topics(:first), :approved?
     topic = topics(:first)
     topic.toggle(:approved)
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
   end
 
   def test_reload
@@ -1431,11 +1431,11 @@ class BasicsTest < ActiveRecord::TestCase
   test "resetting column information doesn't remove attribute methods" do
     topic = topics(:first)
 
-    assert_not topic.id_changed?
+    assert_not_predicate topic, :id_changed?
 
     Topic.reset_column_information
 
-    assert_not topic.id_changed?
+    assert_not_predicate topic, :id_changed?
   end
 
   test "ignored columns are not present in columns_hash" do
@@ -1447,27 +1447,27 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   test "ignored columns have no attribute methods" do
-    refute Developer.new.respond_to?(:first_name)
-    refute Developer.new.respond_to?(:first_name=)
-    refute Developer.new.respond_to?(:first_name?)
-    refute SubDeveloper.new.respond_to?(:first_name)
-    refute SubDeveloper.new.respond_to?(:first_name=)
-    refute SubDeveloper.new.respond_to?(:first_name?)
-    refute SymbolIgnoredDeveloper.new.respond_to?(:first_name)
-    refute SymbolIgnoredDeveloper.new.respond_to?(:first_name=)
-    refute SymbolIgnoredDeveloper.new.respond_to?(:first_name?)
+    assert_not_respond_to Developer.new, :first_name
+    assert_not_respond_to Developer.new, :first_name=
+    assert_not_respond_to Developer.new, :first_name?
+    assert_not_respond_to SubDeveloper.new, :first_name
+    assert_not_respond_to SubDeveloper.new, :first_name=
+    assert_not_respond_to SubDeveloper.new, :first_name?
+    assert_not_respond_to SymbolIgnoredDeveloper.new, :first_name
+    assert_not_respond_to SymbolIgnoredDeveloper.new, :first_name=
+    assert_not_respond_to SymbolIgnoredDeveloper.new, :first_name?
   end
 
   test "ignored columns don't prevent explicit declaration of attribute methods" do
-    assert Developer.new.respond_to?(:last_name)
-    assert Developer.new.respond_to?(:last_name=)
-    assert Developer.new.respond_to?(:last_name?)
-    assert SubDeveloper.new.respond_to?(:last_name)
-    assert SubDeveloper.new.respond_to?(:last_name=)
-    assert SubDeveloper.new.respond_to?(:last_name?)
-    assert SymbolIgnoredDeveloper.new.respond_to?(:last_name)
-    assert SymbolIgnoredDeveloper.new.respond_to?(:last_name=)
-    assert SymbolIgnoredDeveloper.new.respond_to?(:last_name?)
+    assert_respond_to Developer.new, :last_name
+    assert_respond_to Developer.new, :last_name=
+    assert_respond_to Developer.new, :last_name?
+    assert_respond_to SubDeveloper.new, :last_name
+    assert_respond_to SubDeveloper.new, :last_name=
+    assert_respond_to SubDeveloper.new, :last_name?
+    assert_respond_to SymbolIgnoredDeveloper.new, :last_name
+    assert_respond_to SymbolIgnoredDeveloper.new, :last_name=
+    assert_respond_to SymbolIgnoredDeveloper.new, :last_name?
   end
 
   test "ignored columns are stored as an array of string" do
@@ -1477,20 +1477,20 @@ class BasicsTest < ActiveRecord::TestCase
 
   test "when #reload called, ignored columns' attribute methods are not defined" do
     developer = Developer.create!(name: "Developer")
-    refute developer.respond_to?(:first_name)
-    refute developer.respond_to?(:first_name=)
+    assert_not_respond_to developer, :first_name
+    assert_not_respond_to developer, :first_name=
 
     developer.reload
 
-    refute developer.respond_to?(:first_name)
-    refute developer.respond_to?(:first_name=)
+    assert_not_respond_to developer, :first_name
+    assert_not_respond_to developer, :first_name=
   end
 
   test "ignored columns not included in SELECT" do
     query = Developer.all.to_sql.downcase
 
     # ignored column
-    refute query.include?("first_name")
+    assert_not query.include?("first_name")
 
     # regular column
     assert query.include?("name")
@@ -1501,7 +1501,7 @@ class BasicsTest < ActiveRecord::TestCase
     query = Developer.from("developers").to_sql
     quoted_id = "#{Developer.quoted_table_name}.#{Developer.quoted_primary_key}"
 
-    assert_match(/SELECT #{quoted_id}.* FROM developers/, query)
+    assert_match(/SELECT #{Regexp.escape(quoted_id)}.* FROM developers/, query)
   end
 
   test "using table name qualified column names unless having SELECT list explicitly" do
diff --git a/activerecord/test/cases/batches_test.rb b/activerecord/test/cases/batches_test.rb
index be8aeed5ac..c8163901c6 100644
--- a/activerecord/test/cases/batches_test.rb
+++ b/activerecord/test/cases/batches_test.rb
@@ -313,7 +313,7 @@ class EachTest < ActiveRecord::TestCase
   def test_in_batches_each_record_should_yield_record_if_block_is_given
     assert_queries(6) do
       Post.in_batches(of: 2).each_record do |post|
-        assert post.title.present?
+        assert_predicate post.title, :present?
         assert_kind_of Post, post
       end
     end
@@ -322,7 +322,7 @@ class EachTest < ActiveRecord::TestCase
   def test_in_batches_each_record_should_return_enumerator_if_no_block_given
     assert_queries(6) do
       Post.in_batches(of: 2).each_record.with_index do |post, i|
-        assert post.title.present?
+        assert_predicate post.title, :present?
         assert_kind_of Post, post
       end
     end
@@ -353,24 +353,24 @@ class EachTest < ActiveRecord::TestCase
 
   def test_in_batches_should_not_be_loaded
     Post.in_batches(of: 1) do |relation|
-      assert_not relation.loaded?
+      assert_not_predicate relation, :loaded?
     end
 
     Post.in_batches(of: 1, load: false) do |relation|
-      assert_not relation.loaded?
+      assert_not_predicate relation, :loaded?
     end
   end
 
   def test_in_batches_should_be_loaded
     Post.in_batches(of: 1, load: true) do |relation|
-      assert relation.loaded?
+      assert_predicate relation, :loaded?
     end
   end
 
   def test_in_batches_if_not_loaded_executes_more_queries
     assert_queries(@total + 1) do
       Post.in_batches(of: 1, load: false) do |relation|
-        assert_not relation.loaded?
+        assert_not_predicate relation, :loaded?
       end
     end
   end
@@ -508,7 +508,7 @@ class EachTest < ActiveRecord::TestCase
   def test_in_batches_relations_update_all_should_not_affect_matching_records_in_other_batches
     Post.update_all(author_id: 0)
     person = Post.last
-    person.update_attributes(author_id: 1)
+    person.update(author_id: 1)
 
     Post.in_batches(of: 2) do |batch|
       batch.where("author_id >= 1").update_all("author_id = author_id + 1")
@@ -592,7 +592,11 @@ class EachTest < ActiveRecord::TestCase
       table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
       predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
 
-      posts = ActiveRecord::Relation.create(Post, table_alias, predicate_builder)
+      posts = ActiveRecord::Relation.create(
+        Post,
+        table: table_alias,
+        predicate_builder: predicate_builder
+      )
       posts.find_each {}
     end
   end
diff --git a/activerecord/test/cases/cache_key_test.rb b/activerecord/test/cases/cache_key_test.rb
index 8f2f2c6186..3a569f226e 100644
--- a/activerecord/test/cases/cache_key_test.rb
+++ b/activerecord/test/cases/cache_key_test.rb
@@ -38,8 +38,8 @@ module ActiveRecord
     end
 
     test "cache_version is only there when versioning is on" do
-      assert CacheMeWithVersion.create.cache_version.present?
-      assert_not CacheMe.create.cache_version.present?
+      assert_predicate CacheMeWithVersion.create.cache_version, :present?
+      assert_not_predicate CacheMe.create.cache_version, :present?
     end
 
     test "cache_key_with_version always has both key and version" do
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index e682da6fed..0828d6b58f 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -21,7 +21,7 @@ require "models/comment"
 require "models/rating"
 
 class CalculationsTest < ActiveRecord::TestCase
-  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books
+  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books, :posts, :comments
 
   def test_should_sum_field
     assert_equal 318, Account.sum(:credit_limit)
@@ -236,6 +236,12 @@ class CalculationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_count_with_eager_loading_and_custom_order
+    posts = Post.includes(:comments).order("comments.id")
+    assert_queries(1) { assert_equal 11, posts.count }
+    assert_queries(1) { assert_equal 11, posts.count(:all) }
+  end
+
   def test_distinct_count_all_with_custom_select_and_order
     accounts = Account.distinct.select("credit_limit % 10").order(Arel.sql("credit_limit % 10"))
     assert_queries(1) { assert_equal 3, accounts.count(:all) }
@@ -787,6 +793,18 @@ class CalculationsTest < ActiveRecord::TestCase
     end
   end
 
+  def test_pick_one
+    assert_equal "The First Topic", Topic.order(:id).pick(:heading)
+    assert_nil Topic.none.pick(:heading)
+    assert_nil Topic.where("1=0").pick(:heading)
+  end
+
+  def test_pick_two
+    assert_equal ["David", "david@loudthinking.com"], Topic.order(:id).pick(:author_name, :author_email_address)
+    assert_nil Topic.none.pick(:author_name, :author_email_address)
+    assert_nil Topic.where("1=0").pick(:author_name, :author_email_address)
+  end
+
   def test_grouped_calculation_with_polymorphic_relation
     part = ShipPart.create!(name: "has trinket")
     part.trinkets.create!
diff --git a/activerecord/test/cases/callbacks_test.rb b/activerecord/test/cases/callbacks_test.rb
index 55c7475f46..3b283a3aa6 100644
--- a/activerecord/test/cases/callbacks_test.rb
+++ b/activerecord/test/cases/callbacks_test.rb
@@ -394,27 +394,27 @@ class CallbacksTest < ActiveRecord::TestCase
   def test_before_create_throwing_abort
     someone = CallbackHaltedDeveloper.new
     someone.cancel_before_create = true
-    assert someone.valid?
+    assert_predicate someone, :valid?
     assert !someone.save
     assert_save_callbacks_not_called(someone)
   end
 
   def test_before_save_throwing_abort
     david = DeveloperWithCanceledCallbacks.find(1)
-    assert david.valid?
+    assert_predicate david, :valid?
     assert !david.save
     exc = assert_raise(ActiveRecord::RecordNotSaved) { david.save! }
     assert_equal david, exc.record
 
     david = DeveloperWithCanceledCallbacks.find(1)
     david.salary = 10_000_000
-    assert !david.valid?
+    assert_not_predicate david, :valid?
     assert !david.save
     assert_raise(ActiveRecord::RecordInvalid) { david.save! }
 
     someone = CallbackHaltedDeveloper.find(1)
     someone.cancel_before_save = true
-    assert someone.valid?
+    assert_predicate someone, :valid?
     assert !someone.save
     assert_save_callbacks_not_called(someone)
   end
@@ -422,7 +422,7 @@ class CallbacksTest < ActiveRecord::TestCase
   def test_before_update_throwing_abort
     someone = CallbackHaltedDeveloper.find(1)
     someone.cancel_before_update = true
-    assert someone.valid?
+    assert_predicate someone, :valid?
     assert !someone.save
     assert_save_callbacks_not_called(someone)
   end
diff --git a/activerecord/test/cases/clone_test.rb b/activerecord/test/cases/clone_test.rb
index 3187e6aed5..65e5016040 100644
--- a/activerecord/test/cases/clone_test.rb
+++ b/activerecord/test/cases/clone_test.rb
@@ -36,7 +36,7 @@ module ActiveRecord
       cloned = Topic.new
       clone = cloned.clone
       cloned.freeze
-      assert_not clone.frozen?
+      assert_not_predicate clone, :frozen?
     end
   end
 end
diff --git a/activerecord/test/cases/collection_cache_key_test.rb b/activerecord/test/cases/collection_cache_key_test.rb
index cfe95b2360..a5d908344a 100644
--- a/activerecord/test/cases/collection_cache_key_test.rb
+++ b/activerecord/test/cases/collection_cache_key_test.rb
@@ -60,7 +60,11 @@ module ActiveRecord
       table_metadata = ActiveRecord::TableMetadata.new(Developer, table_alias)
       predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
 
-      developers = ActiveRecord::Relation.create(Developer, table_alias, predicate_builder)
+      developers = ActiveRecord::Relation.create(
+        Developer,
+        table: table_alias,
+        predicate_builder: predicate_builder
+      )
       developers = developers.where(salary: 100000).order(updated_at: :desc)
       last_developer_timestamp = developers.first.updated_at
 
diff --git a/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb b/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
index 82c6cf8dea..72838ff56b 100644
--- a/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
+++ b/activerecord/test/cases/connection_adapters/adapter_leasing_test.rb
@@ -45,11 +45,11 @@ module ActiveRecord
 
         # Make sure the pool marks the connection in use
         assert_equal @adapter, pool.connection
-        assert @adapter.in_use?
+        assert_predicate @adapter, :in_use?
 
         # Close should put the adapter back in the pool
         @adapter.close
-        assert_not @adapter.in_use?
+        assert_not_predicate @adapter, :in_use?
 
         assert_equal @adapter, pool.connection
       end
diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index 603ed63a8c..f4cc251fb9 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -103,11 +103,11 @@ module ActiveRecord
       end
 
       def test_active_connections?
-        assert !@handler.active_connections?
+        assert_not_predicate @handler, :active_connections?
         assert @handler.retrieve_connection(@spec_name)
-        assert @handler.active_connections?
+        assert_predicate @handler, :active_connections?
         @handler.clear_active_connections!
-        assert !@handler.active_connections?
+        assert_not_predicate @handler, :active_connections?
       end
 
       def test_retrieve_connection_pool
@@ -146,7 +146,7 @@ module ActiveRecord
 
         def test_forked_child_doesnt_mangle_parent_connection
           object_id = ActiveRecord::Base.connection.object_id
-          assert ActiveRecord::Base.connection.active?
+          assert_predicate ActiveRecord::Base.connection, :active?
 
           rd, wr = IO.pipe
           rd.binmode
@@ -171,6 +171,48 @@ module ActiveRecord
           assert_equal 3, ActiveRecord::Base.connection.select_value("SELECT COUNT(*) FROM people")
         end
 
+        unless in_memory_db?
+          def test_forked_child_recovers_from_disconnected_parent
+            object_id = ActiveRecord::Base.connection.object_id
+            assert_predicate ActiveRecord::Base.connection, :active?
+
+            rd, wr = IO.pipe
+            rd.binmode
+            wr.binmode
+
+            outer_pid = fork {
+              ActiveRecord::Base.connection.disconnect!
+
+              pid = fork {
+                rd.close
+                if ActiveRecord::Base.connection.active?
+                  pair = [ActiveRecord::Base.connection.object_id,
+                          ActiveRecord::Base.connection.select_value("SELECT COUNT(*) FROM people")]
+                  wr.write Marshal.dump pair
+                end
+                wr.close
+
+                exit # allow finalizers to run
+              }
+
+              Process.waitpid pid
+            }
+
+            wr.close
+
+            Process.waitpid outer_pid
+            child_id, child_count = Marshal.load(rd.read)
+
+            assert_not_equal object_id, child_id
+            rd.close
+
+            assert_equal 3, child_count
+
+            # Outer connection is unaffected
+            assert_equal 6, ActiveRecord::Base.connection.select_value("SELECT 2 * COUNT(*) FROM people")
+          end
+        end
+
         def test_retrieve_connection_pool_copies_schema_cache_from_ancestor_pool
           @pool.schema_cache = @pool.connection.schema_cache
           @pool.schema_cache.add("posts")
diff --git a/activerecord/test/cases/connection_adapters/schema_cache_test.rb b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
index 006be9e65d..67496381d1 100644
--- a/activerecord/test/cases/connection_adapters/schema_cache_test.rb
+++ b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
@@ -22,8 +22,8 @@ module ActiveRecord
 
         new_cache = YAML.load(YAML.dump(@cache))
         assert_no_queries do
-          assert_equal 11, new_cache.columns("posts").size
-          assert_equal 11, new_cache.columns_hash("posts").size
+          assert_equal 12, new_cache.columns("posts").size
+          assert_equal 12, new_cache.columns_hash("posts").size
           assert new_cache.data_sources("posts")
           assert_equal "id", new_cache.primary_keys("posts")
         end
@@ -75,8 +75,8 @@ module ActiveRecord
         @cache = Marshal.load(Marshal.dump(@cache))
 
         assert_no_queries do
-          assert_equal 11, @cache.columns("posts").size
-          assert_equal 11, @cache.columns_hash("posts").size
+          assert_equal 12, @cache.columns("posts").size
+          assert_equal 12, @cache.columns_hash("posts").size
           assert @cache.data_sources("posts")
           assert_equal "id", @cache.primary_keys("posts")
         end
diff --git a/activerecord/test/cases/connection_management_test.rb b/activerecord/test/cases/connection_management_test.rb
index 9d6ecbde78..0941ee3309 100644
--- a/activerecord/test/cases/connection_management_test.rb
+++ b/activerecord/test/cases/connection_management_test.rb
@@ -27,7 +27,7 @@ module ActiveRecord
 
         # make sure we have an active connection
         assert ActiveRecord::Base.connection
-        assert ActiveRecord::Base.connection_handler.active_connections?
+        assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
       end
 
       def test_app_delegation
@@ -47,14 +47,14 @@ module ActiveRecord
       def test_connections_are_cleared_after_body_close
         _, _, body = @management.call(@env)
         body.close
-        assert !ActiveRecord::Base.connection_handler.active_connections?
+        assert_not_predicate ActiveRecord::Base.connection_handler, :active_connections?
       end
 
       def test_active_connections_are_not_cleared_on_body_close_during_transaction
         ActiveRecord::Base.transaction do
           _, _, body = @management.call(@env)
           body.close
-          assert ActiveRecord::Base.connection_handler.active_connections?
+          assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
         end
       end
 
@@ -62,7 +62,7 @@ module ActiveRecord
         app       = Class.new(App) { def call(env); raise NotImplementedError; end }.new
         explosive = middleware(app)
         assert_raises(NotImplementedError) { explosive.call(@env) }
-        assert !ActiveRecord::Base.connection_handler.active_connections?
+        assert_not_predicate ActiveRecord::Base.connection_handler, :active_connections?
       end
 
       def test_connections_not_closed_if_exception_inside_transaction
@@ -70,14 +70,14 @@ module ActiveRecord
           app               = Class.new(App) { def call(env); raise RuntimeError; end }.new
           explosive         = middleware(app)
           assert_raises(RuntimeError) { explosive.call(@env) }
-          assert ActiveRecord::Base.connection_handler.active_connections?
+          assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
         end
       end
 
       test "doesn't clear active connections when running in a test case" do
         executor.wrap do
           @management.call(@env)
-          assert ActiveRecord::Base.connection_handler.active_connections?
+          assert_predicate ActiveRecord::Base.connection_handler, :active_connections?
         end
       end
 
@@ -85,7 +85,7 @@ module ActiveRecord
         body = Class.new(String) { def to_path; "/path"; end }.new
         app = lambda { |_| [200, {}, body] }
         response_body = middleware(app).call(@env)[2]
-        assert response_body.respond_to?(:to_path)
+        assert_respond_to response_body, :to_path
         assert_equal "/path", response_body.to_path
       end
 
diff --git a/activerecord/test/cases/connection_pool_test.rb b/activerecord/test/cases/connection_pool_test.rb
index cb29c578b7..bfaaa3c54e 100644
--- a/activerecord/test/cases/connection_pool_test.rb
+++ b/activerecord/test/cases/connection_pool_test.rb
@@ -35,12 +35,12 @@ module ActiveRecord
 
       def test_checkout_after_close
         connection = pool.connection
-        assert connection.in_use?
+        assert_predicate connection, :in_use?
 
         connection.close
-        assert !connection.in_use?
+        assert_not_predicate connection, :in_use?
 
-        assert pool.connection.in_use?
+        assert_predicate pool.connection, :in_use?
       end
 
       def test_released_connection_moves_between_threads
@@ -80,14 +80,14 @@ module ActiveRecord
       end
 
       def test_active_connection_in_use
-        assert !pool.active_connection?
+        assert_not_predicate pool, :active_connection?
         main_thread = pool.connection
 
-        assert pool.active_connection?
+        assert_predicate pool, :active_connection?
 
         main_thread.close
 
-        assert !pool.active_connection?
+        assert_not_predicate pool, :active_connection?
       end
 
       def test_full_pool_exception
@@ -205,11 +205,11 @@ module ActiveRecord
 
       def test_remove_connection
         conn = @pool.checkout
-        assert conn.in_use?
+        assert_predicate conn, :in_use?
 
         length = @pool.connections.length
         @pool.remove conn
-        assert conn.in_use?
+        assert_predicate conn, :in_use?
         assert_equal(length - 1, @pool.connections.length)
       ensure
         conn.close
@@ -224,11 +224,11 @@ module ActiveRecord
       end
 
       def test_active_connection?
-        assert !@pool.active_connection?
+        assert_not_predicate @pool, :active_connection?
         assert @pool.connection
-        assert @pool.active_connection?
+        assert_predicate @pool, :active_connection?
         @pool.release_connection
-        assert !@pool.active_connection?
+        assert_not_predicate @pool, :active_connection?
       end
 
       def test_checkout_behaviour
@@ -496,7 +496,7 @@ module ActiveRecord
               assert_nil timed_join_result
 
               # assert that since this is within default timeout our connection hasn't been forcefully taken away from us
-              assert @pool.active_connection?
+              assert_predicate @pool, :active_connection?
             end
           ensure
             thread.join if thread && !timed_join_result # clean up the other thread
@@ -510,7 +510,7 @@ module ActiveRecord
           @pool.with_connection do |connection|
             Thread.new { @pool.send(group_action_method) }.join
             # assert connection has been forcefully taken away from us
-            assert_not @pool.active_connection?
+            assert_not_predicate @pool, :active_connection?
 
             # make a new connection for with_connection to clean up
             @pool.connection
diff --git a/activerecord/test/cases/core_test.rb b/activerecord/test/cases/core_test.rb
index 356afdbd2b..6e7ae2efb4 100644
--- a/activerecord/test/cases/core_test.rb
+++ b/activerecord/test/cases/core_test.rb
@@ -4,7 +4,6 @@ require "cases/helper"
 require "models/person"
 require "models/topic"
 require "pp"
-require "active_support/core_ext/string/strip"
 
 class NonExistentTable < ActiveRecord::Base; end
 
@@ -39,26 +38,26 @@ class CoreTest < ActiveRecord::TestCase
     topic = Topic.new
     actual = "".dup
     PP.pp(topic, StringIO.new(actual))
-    expected = <<-PRETTY.strip_heredoc
-    #<Topic:0xXXXXXX
-     id: nil,
-     title: nil,
-     author_name: nil,
-     author_email_address: "test@test.com",
-     written_on: nil,
-     bonus_time: nil,
-     last_read: nil,
-     content: nil,
-     important: nil,
-     approved: true,
-     replies_count: 0,
-     unique_replies_count: 0,
-     parent_id: nil,
-     parent_title: nil,
-     type: nil,
-     group: nil,
-     created_at: nil,
-     updated_at: nil>
+    expected = <<~PRETTY
+      #<Topic:0xXXXXXX
+       id: nil,
+       title: nil,
+       author_name: nil,
+       author_email_address: "test@test.com",
+       written_on: nil,
+       bonus_time: nil,
+       last_read: nil,
+       content: nil,
+       important: nil,
+       approved: true,
+       replies_count: 0,
+       unique_replies_count: 0,
+       parent_id: nil,
+       parent_title: nil,
+       type: nil,
+       group: nil,
+       created_at: nil,
+       updated_at: nil>
     PRETTY
     assert actual.start_with?(expected.split("XXXXXX").first)
     assert actual.end_with?(expected.split("XXXXXX").last)
@@ -68,26 +67,26 @@ class CoreTest < ActiveRecord::TestCase
     topic = topics(:first)
     actual = "".dup
     PP.pp(topic, StringIO.new(actual))
-    expected = <<-PRETTY.strip_heredoc
-    #<Topic:0x\\w+
-     id: 1,
-     title: "The First Topic",
-     author_name: "David",
-     author_email_address: "david@loudthinking.com",
-     written_on: 2003-07-16 14:28:11 UTC,
-     bonus_time: 2000-01-01 14:28:00 UTC,
-     last_read: Thu, 15 Apr 2004,
-     content: "Have a nice day",
-     important: nil,
-     approved: false,
-     replies_count: 1,
-     unique_replies_count: 0,
-     parent_id: nil,
-     parent_title: nil,
-     type: nil,
-     group: nil,
-     created_at: [^,]+,
-     updated_at: [^,>]+>
+    expected = <<~PRETTY
+      #<Topic:0x\\w+
+       id: 1,
+       title: "The First Topic",
+       author_name: "David",
+       author_email_address: "david@loudthinking.com",
+       written_on: 2003-07-16 14:28:11 UTC,
+       bonus_time: 2000-01-01 14:28:00 UTC,
+       last_read: Thu, 15 Apr 2004,
+       content: "Have a nice day",
+       important: nil,
+       approved: false,
+       replies_count: 1,
+       unique_replies_count: 0,
+       parent_id: nil,
+       parent_title: nil,
+       type: nil,
+       group: nil,
+       created_at: [^,]+,
+       updated_at: [^,>]+>
     PRETTY
     assert_match(/\A#{expected}\z/, actual)
   end
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index d4408776d3..14c4e3cbd4 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -24,18 +24,18 @@ class DirtyTest < ActiveRecord::TestCase
 
     # Change catchphrase.
     pirate.catchphrase = "arrr"
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     assert_nil pirate.catchphrase_was
     assert_equal [nil, "arrr"], pirate.catchphrase_change
 
     # Saved - no changes.
     pirate.save!
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
     assert_nil pirate.catchphrase_change
 
     # Same value - no changes.
     pirate.catchphrase = "arrr"
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
     assert_nil pirate.catchphrase_change
   end
 
@@ -46,23 +46,23 @@ class DirtyTest < ActiveRecord::TestCase
 
       # New record - no changes.
       pirate = target.new
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Saved - no changes.
       pirate.catchphrase = "arrrr, time zone!!"
       pirate.save!
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Change created_on.
       old_created_on = pirate.created_on
       pirate.created_on = Time.now - 1.day
-      assert pirate.created_on_changed?
+      assert_predicate pirate, :created_on_changed?
       assert_kind_of ActiveSupport::TimeWithZone, pirate.created_on_was
       assert_equal old_created_on, pirate.created_on_was
       pirate.created_on = old_created_on
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
     end
   end
 
@@ -73,7 +73,7 @@ class DirtyTest < ActiveRecord::TestCase
 
       pirate = target.create!
       pirate.created_on = pirate.created_on
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
     end
   end
 
@@ -86,19 +86,19 @@ class DirtyTest < ActiveRecord::TestCase
 
       # New record - no changes.
       pirate = target.new
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Saved - no changes.
       pirate.catchphrase = "arrrr, time zone!!"
       pirate.save!
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Change created_on.
       old_created_on = pirate.created_on
       pirate.created_on = Time.now + 1.day
-      assert pirate.created_on_changed?
+      assert_predicate pirate, :created_on_changed?
       # kind_of does not work because
       # ActiveSupport::TimeWithZone.name == 'Time'
       assert_instance_of Time, pirate.created_on_was
@@ -113,19 +113,19 @@ class DirtyTest < ActiveRecord::TestCase
 
       # New record - no changes.
       pirate = target.new
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Saved - no changes.
       pirate.catchphrase = "arrrr, time zone!!"
       pirate.save!
-      assert !pirate.created_on_changed?
+      assert_not_predicate pirate, :created_on_changed?
       assert_nil pirate.created_on_change
 
       # Change created_on.
       old_created_on = pirate.created_on
       pirate.created_on = Time.now + 1.day
-      assert pirate.created_on_changed?
+      assert_predicate pirate, :created_on_changed?
       # kind_of does not work because
       # ActiveSupport::TimeWithZone.name == 'Time'
       assert_instance_of Time, pirate.created_on_was
@@ -137,11 +137,11 @@ class DirtyTest < ActiveRecord::TestCase
     # the actual attribute here is name, title is an
     # alias setup via alias_attribute
     parrot = Parrot.new
-    assert !parrot.title_changed?
+    assert_not_predicate parrot, :title_changed?
     assert_nil parrot.title_change
 
     parrot.name = "Sam"
-    assert parrot.title_changed?
+    assert_predicate parrot, :title_changed?
     assert_nil parrot.title_was
     assert_equal parrot.name_change, parrot.title_change
   end
@@ -153,7 +153,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.restore_catchphrase!
     assert_equal "Yar!", pirate.catchphrase
     assert_equal Hash.new, pirate.changes
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
   end
 
   def test_nullable_number_not_marked_as_changed_if_new_value_is_blank
@@ -161,7 +161,7 @@ class DirtyTest < ActiveRecord::TestCase
 
     ["", nil].each do |value|
       pirate.parrot_id = value
-      assert !pirate.parrot_id_changed?
+      assert_not_predicate pirate, :parrot_id_changed?
       assert_nil pirate.parrot_id_change
     end
   end
@@ -171,7 +171,7 @@ class DirtyTest < ActiveRecord::TestCase
 
     ["", nil].each do |value|
       numeric_data.bank_balance = value
-      assert !numeric_data.bank_balance_changed?
+      assert_not_predicate numeric_data, :bank_balance_changed?
       assert_nil numeric_data.bank_balance_change
     end
   end
@@ -181,7 +181,7 @@ class DirtyTest < ActiveRecord::TestCase
 
     ["", nil].each do |value|
       numeric_data.temperature = value
-      assert !numeric_data.temperature_changed?
+      assert_not_predicate numeric_data, :temperature_changed?
       assert_nil numeric_data.temperature_change
     end
   end
@@ -197,7 +197,7 @@ class DirtyTest < ActiveRecord::TestCase
       ["", nil].each do |value|
         topic.written_on = value
         assert_nil topic.written_on
-        assert !topic.written_on_changed?
+        assert_not_predicate topic, :written_on_changed?
       end
     end
   end
@@ -208,10 +208,10 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.catchphrase = "arrr"
     assert pirate.save!
 
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
 
     pirate.parrot_id = "0"
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_integer_zero_to_integer_zero_not_marked_as_changed
@@ -220,17 +220,17 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.catchphrase = "arrr"
     assert pirate.save!
 
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
 
     pirate.parrot_id = 0
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_float_zero_to_string_zero_not_marked_as_changed
     data = NumericData.new temperature: 0.0
     data.save!
 
-    assert_not data.changed?
+    assert_not_predicate data, :changed?
 
     data.temperature = "0"
     assert_empty data.changes
@@ -251,38 +251,38 @@ class DirtyTest < ActiveRecord::TestCase
     # check the change from 1 to ''
     pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
     pirate.parrot_id = ""
-    assert pirate.parrot_id_changed?
+    assert_predicate pirate, :parrot_id_changed?
     assert_equal([1, nil], pirate.parrot_id_change)
     pirate.save
 
     # check the change from nil to 0
     pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
     pirate.parrot_id = 0
-    assert pirate.parrot_id_changed?
+    assert_predicate pirate, :parrot_id_changed?
     assert_equal([nil, 0], pirate.parrot_id_change)
     pirate.save
 
     # check the change from 0 to ''
     pirate = Pirate.find_by_catchphrase("Yarrrr, me hearties")
     pirate.parrot_id = ""
-    assert pirate.parrot_id_changed?
+    assert_predicate pirate, :parrot_id_changed?
     assert_equal([0, nil], pirate.parrot_id_change)
   end
 
   def test_object_should_be_changed_if_any_attribute_is_changed
     pirate = Pirate.new
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
     assert_equal [], pirate.changed
     assert_equal Hash.new, pirate.changes
 
     pirate.catchphrase = "arrr"
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     assert_nil pirate.catchphrase_was
     assert_equal %w(catchphrase), pirate.changed
     assert_equal({ "catchphrase" => [nil, "arrr"] }, pirate.changes)
 
     pirate.save
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
     assert_equal [], pirate.changed
     assert_equal Hash.new, pirate.changes
   end
@@ -290,40 +290,40 @@ class DirtyTest < ActiveRecord::TestCase
   def test_attribute_will_change!
     pirate = Pirate.create!(catchphrase: "arr")
 
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
     assert pirate.catchphrase_will_change!
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     assert_equal ["arr", "arr"], pirate.catchphrase_change
 
     pirate.catchphrase << " matey!"
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     assert_equal ["arr", "arr matey!"], pirate.catchphrase_change
   end
 
   def test_virtual_attribute_will_change
     parrot = Parrot.create!(name: "Ruby")
     parrot.send(:attribute_will_change!, :cancel_save_from_callback)
-    assert parrot.has_changes_to_save?
+    assert_predicate parrot, :has_changes_to_save?
   end
 
   def test_association_assignment_changes_foreign_key
     pirate = Pirate.create!(catchphrase: "jarl")
     pirate.parrot = Parrot.create!(name: "Lorre")
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     assert_equal %w(parrot_id), pirate.changed
   end
 
   def test_attribute_should_be_compared_with_type_cast
     topic = Topic.new
-    assert topic.approved?
-    assert !topic.approved_changed?
+    assert_predicate topic, :approved?
+    assert_not_predicate topic, :approved_changed?
 
     # Coming from web form.
     params = { topic: { approved: 1 } }
     # In the controller.
     topic.attributes = params[:topic]
-    assert topic.approved?
-    assert !topic.approved_changed?
+    assert_predicate topic, :approved?
+    assert_not_predicate topic, :approved_changed?
   end
 
   def test_partial_update
@@ -378,9 +378,9 @@ class DirtyTest < ActiveRecord::TestCase
   def test_reload_should_clear_changed_attributes
     pirate = Pirate.create!(catchphrase: "shiver me timbers")
     pirate.catchphrase = "*hic*"
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     pirate.reload
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_dup_objects_should_not_copy_dirty_flag_from_creator
@@ -388,17 +388,17 @@ class DirtyTest < ActiveRecord::TestCase
     pirate_dup = pirate.dup
     pirate_dup.restore_catchphrase!
     pirate.catchphrase = "I love Rum"
-    assert pirate.catchphrase_changed?
-    assert !pirate_dup.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
+    assert_not_predicate pirate_dup, :catchphrase_changed?
   end
 
   def test_reverted_changes_are_not_dirty
     phrase = "shiver me timbers"
     pirate = Pirate.create!(catchphrase: phrase)
     pirate.catchphrase = "*hic*"
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     pirate.catchphrase = phrase
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_reverted_changes_are_not_dirty_after_multiple_changes
@@ -406,40 +406,40 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.create!(catchphrase: phrase)
     10.times do |i|
       pirate.catchphrase = "*hic*" * i
-      assert pirate.changed?
+      assert_predicate pirate, :changed?
     end
-    assert pirate.changed?
+    assert_predicate pirate, :changed?
     pirate.catchphrase = phrase
-    assert !pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   def test_reverted_changes_are_not_dirty_going_from_nil_to_value_and_back
     pirate = Pirate.create!(catchphrase: "Yar!")
 
     pirate.parrot_id = 1
-    assert pirate.changed?
-    assert pirate.parrot_id_changed?
-    assert !pirate.catchphrase_changed?
+    assert_predicate pirate, :changed?
+    assert_predicate pirate, :parrot_id_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
 
     pirate.parrot_id = nil
-    assert !pirate.changed?
-    assert !pirate.parrot_id_changed?
-    assert !pirate.catchphrase_changed?
+    assert_not_predicate pirate, :changed?
+    assert_not_predicate pirate, :parrot_id_changed?
+    assert_not_predicate pirate, :catchphrase_changed?
   end
 
   def test_save_should_store_serialized_attributes_even_with_partial_writes
     with_partial_writes(Topic) do
       topic = Topic.create!(content: { a: "a" })
 
-      assert_not topic.changed?
+      assert_not_predicate topic, :changed?
 
       topic.content[:b] = "b"
 
-      assert topic.changed?
+      assert_predicate topic, :changed?
 
       topic.save!
 
-      assert_not topic.changed?
+      assert_not_predicate topic, :changed?
       assert_equal "b", topic.content[:b]
 
       topic.reload
@@ -596,7 +596,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.create!(catchphrase: "rrrr", created_on: time_in_paris)
 
     pirate.created_on = pirate.created_on.in_time_zone("Tokyo").to_s
-    assert !pirate.created_on_changed?
+    assert_not_predicate pirate, :created_on_changed?
   end
 
   test "partial insert" do
@@ -627,7 +627,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate = Pirate.create!(catchphrase: "arrrr")
     pirate.catchphrase << " matey!"
 
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
     expected_changes = {
       "catchphrase" => ["arrrr", "arrrr matey!"]
     }
@@ -641,7 +641,7 @@ class DirtyTest < ActiveRecord::TestCase
     pirate.reload
 
     assert_equal "arrrr matey!", pirate.catchphrase
-    assert_not pirate.changed?
+    assert_not_predicate pirate, :changed?
   end
 
   test "in place mutation for binary" do
@@ -652,19 +652,19 @@ class DirtyTest < ActiveRecord::TestCase
 
     binary = klass.create!(data: "\\\\foo")
 
-    assert_not binary.changed?
+    assert_not_predicate binary, :changed?
 
     binary.data = binary.data.dup
 
-    assert_not binary.changed?
+    assert_not_predicate binary, :changed?
 
     binary = klass.last
 
-    assert_not binary.changed?
+    assert_not_predicate binary, :changed?
 
     binary.data << "bar"
 
-    assert binary.changed?
+    assert_predicate binary, :changed?
   end
 
   test "changes is correct for subclass" do
@@ -679,7 +679,7 @@ class DirtyTest < ActiveRecord::TestCase
     new_catchphrase = "arrrr matey!"
 
     pirate.catchphrase = new_catchphrase
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
 
     expected_changes = {
       "catchphrase" => ["arrrr", new_catchphrase]
@@ -698,7 +698,7 @@ class DirtyTest < ActiveRecord::TestCase
     new_catchphrase = "arrrr matey!"
 
     pirate.catchphrase = new_catchphrase
-    assert pirate.catchphrase_changed?
+    assert_predicate pirate, :catchphrase_changed?
 
     expected_changes = {
       "catchphrase" => ["arrrr", new_catchphrase]
@@ -720,7 +720,7 @@ class DirtyTest < ActiveRecord::TestCase
     end
 
     model = klass.new(first_name: "Jim")
-    assert model.first_name_changed?
+    assert_predicate model, :first_name_changed?
   end
 
   test "attribute_will_change! doesn't try to save non-persistable attributes" do
@@ -732,7 +732,7 @@ class DirtyTest < ActiveRecord::TestCase
     record = klass.new(first_name: "Sean")
     record.non_persisted_attribute_will_change!
 
-    assert record.non_persisted_attribute_changed?
+    assert_predicate record, :non_persisted_attribute_changed?
     assert record.save
   end
 
@@ -762,13 +762,13 @@ class DirtyTest < ActiveRecord::TestCase
 
   test "attributes assigned but not selected are dirty" do
     person = Person.select(:id).first
-    refute person.changed?
+    assert_not_predicate person, :changed?
 
     person.first_name = "Sean"
-    assert person.changed?
+    assert_predicate person, :changed?
 
     person.first_name = nil
-    assert person.changed?
+    assert_predicate person, :changed?
   end
 
   test "attributes not selected are still missing after save" do
@@ -781,14 +781,14 @@ class DirtyTest < ActiveRecord::TestCase
   test "saved_change_to_attribute? returns whether a change occurred in the last save" do
     person = Person.create!(first_name: "Sean")
 
-    assert person.saved_change_to_first_name?
-    refute person.saved_change_to_gender?
+    assert_predicate person, :saved_change_to_first_name?
+    assert_not_predicate person, :saved_change_to_gender?
     assert person.saved_change_to_first_name?(from: nil, to: "Sean")
     assert person.saved_change_to_first_name?(from: nil)
     assert person.saved_change_to_first_name?(to: "Sean")
-    refute person.saved_change_to_first_name?(from: "Jim", to: "Sean")
-    refute person.saved_change_to_first_name?(from: "Jim")
-    refute person.saved_change_to_first_name?(to: "Jim")
+    assert_not person.saved_change_to_first_name?(from: "Jim", to: "Sean")
+    assert_not person.saved_change_to_first_name?(from: "Jim")
+    assert_not person.saved_change_to_first_name?(to: "Jim")
   end
 
   test "saved_change_to_attribute returns the change that occurred in the last save" do
@@ -823,11 +823,11 @@ class DirtyTest < ActiveRecord::TestCase
   test "saved_changes? returns whether the last call to save changed anything" do
     person = Person.create!(first_name: "Sean")
 
-    assert person.saved_changes?
+    assert_predicate person, :saved_changes?
 
     person.save
 
-    refute person.saved_changes?
+    assert_not_predicate person, :saved_changes?
   end
 
   test "saved_changes returns a hash of all the changes that occurred" do
@@ -857,7 +857,7 @@ class DirtyTest < ActiveRecord::TestCase
     end
 
     person = klass.create!(first_name: "Sean")
-    refute person.changed?
+    assert_not_predicate person, :changed?
   end
 
   private
@@ -870,8 +870,8 @@ class DirtyTest < ActiveRecord::TestCase
     end
 
     def check_pirate_after_save_failure(pirate)
-      assert pirate.changed?
-      assert pirate.parrot_id_changed?
+      assert_predicate pirate, :changed?
+      assert_predicate pirate, :parrot_id_changed?
       assert_equal %w(parrot_id), pirate.changed
       assert_nil pirate.parrot_id_was
     end
diff --git a/activerecord/test/cases/dup_test.rb b/activerecord/test/cases/dup_test.rb
index 73da31996e..9e33c3110c 100644
--- a/activerecord/test/cases/dup_test.rb
+++ b/activerecord/test/cases/dup_test.rb
@@ -3,13 +3,14 @@
 require "cases/helper"
 require "models/reply"
 require "models/topic"
+require "models/movie"
 
 module ActiveRecord
   class DupTest < ActiveRecord::TestCase
     fixtures :topics
 
     def test_dup
-      assert !Topic.new.freeze.dup.frozen?
+      assert_not_predicate Topic.new.freeze.dup, :frozen?
     end
 
     def test_not_readonly
@@ -40,7 +41,7 @@ module ActiveRecord
       topic.destroy
 
       duped = topic.dup
-      assert_not duped.destroyed?
+      assert_not_predicate duped, :destroyed?
     end
 
     def test_dup_has_no_id
@@ -126,12 +127,12 @@ module ActiveRecord
 
         duped = topic.dup
         duped.title = nil
-        assert duped.invalid?
+        assert_predicate duped, :invalid?
 
         topic.title = nil
         duped.title = "Mathematics"
-        assert topic.invalid?
-        assert duped.valid?
+        assert_predicate topic, :invalid?
+        assert_predicate duped, :valid?
       end
     end
 
@@ -157,5 +158,20 @@ module ActiveRecord
         record.dup
       end
     end
+
+    def test_dup_record_not_persisted_after_rollback_transaction
+      movie = Movie.new(name: "test")
+
+      assert_raises(ActiveRecord::RecordInvalid) do
+        Movie.transaction do
+          movie.save!
+          duped = movie.dup
+          duped.name = nil
+          duped.save!
+        end
+      end
+
+      assert !movie.persisted?
+    end
   end
 end
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 7cda712112..d5a1d11e12 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -12,16 +12,16 @@ class EnumTest < ActiveRecord::TestCase
   end
 
   test "query state by predicate" do
-    assert @book.published?
-    assert_not @book.written?
-    assert_not @book.proposed?
+    assert_predicate @book, :published?
+    assert_not_predicate @book, :written?
+    assert_not_predicate @book, :proposed?
 
-    assert @book.read?
-    assert @book.in_english?
-    assert @book.author_visibility_visible?
-    assert @book.illustrator_visibility_visible?
-    assert @book.with_medium_font_size?
-    assert @book.medium_to_read?
+    assert_predicate @book, :read?
+    assert_predicate @book, :in_english?
+    assert_predicate @book, :author_visibility_visible?
+    assert_predicate @book, :illustrator_visibility_visible?
+    assert_predicate @book, :with_medium_font_size?
+    assert_predicate @book, :medium_to_read?
   end
 
   test "query state with strings" do
@@ -76,46 +76,46 @@ class EnumTest < ActiveRecord::TestCase
   end
 
   test "build from scope" do
-    assert Book.written.build.written?
-    assert_not Book.written.build.proposed?
+    assert_predicate Book.written.build, :written?
+    assert_not_predicate Book.written.build, :proposed?
   end
 
   test "build from where" do
-    assert Book.where(status: Book.statuses[:written]).build.written?
-    assert_not Book.where(status: Book.statuses[:written]).build.proposed?
-    assert Book.where(status: :written).build.written?
-    assert_not Book.where(status: :written).build.proposed?
-    assert Book.where(status: "written").build.written?
-    assert_not Book.where(status: "written").build.proposed?
+    assert_predicate Book.where(status: Book.statuses[:written]).build, :written?
+    assert_not_predicate Book.where(status: Book.statuses[:written]).build, :proposed?
+    assert_predicate Book.where(status: :written).build, :written?
+    assert_not_predicate Book.where(status: :written).build, :proposed?
+    assert_predicate Book.where(status: "written").build, :written?
+    assert_not_predicate Book.where(status: "written").build, :proposed?
   end
 
   test "update by declaration" do
     @book.written!
-    assert @book.written?
+    assert_predicate @book, :written?
     @book.in_english!
-    assert @book.in_english?
+    assert_predicate @book, :in_english?
     @book.author_visibility_visible!
-    assert @book.author_visibility_visible?
+    assert_predicate @book, :author_visibility_visible?
   end
 
   test "update by setter" do
     @book.update! status: :written
-    assert @book.written?
+    assert_predicate @book, :written?
   end
 
   test "enum methods are overwritable" do
     assert_equal "do publish work...", @book.published!
-    assert @book.published?
+    assert_predicate @book, :published?
   end
 
   test "direct assignment" do
     @book.status = :written
-    assert @book.written?
+    assert_predicate @book, :written?
   end
 
   test "assign string value" do
     @book.status = "written"
-    assert @book.written?
+    assert_predicate @book, :written?
   end
 
   test "enum changed attributes" do
@@ -242,17 +242,17 @@ class EnumTest < ActiveRecord::TestCase
   end
 
   test "building new objects with enum scopes" do
-    assert Book.written.build.written?
-    assert Book.read.build.read?
-    assert Book.in_spanish.build.in_spanish?
-    assert Book.illustrator_visibility_invisible.build.illustrator_visibility_invisible?
+    assert_predicate Book.written.build, :written?
+    assert_predicate Book.read.build, :read?
+    assert_predicate Book.in_spanish.build, :in_spanish?
+    assert_predicate Book.illustrator_visibility_invisible.build, :illustrator_visibility_invisible?
   end
 
   test "creating new objects with enum scopes" do
-    assert Book.written.create.written?
-    assert Book.read.create.read?
-    assert Book.in_spanish.create.in_spanish?
-    assert Book.illustrator_visibility_invisible.create.illustrator_visibility_invisible?
+    assert_predicate Book.written.create, :written?
+    assert_predicate Book.read.create, :read?
+    assert_predicate Book.in_spanish.create, :in_spanish?
+    assert_predicate Book.illustrator_visibility_invisible.create, :illustrator_visibility_invisible?
   end
 
   test "_before_type_cast" do
@@ -355,9 +355,9 @@ class EnumTest < ActiveRecord::TestCase
     klass.delete_all
     klass.create!(status: "proposed")
     book = klass.new(status: "written")
-    assert book.valid?
+    assert_predicate book, :valid?
     book.status = "proposed"
-    assert_not book.valid?
+    assert_not_predicate book, :valid?
   end
 
   test "validate inclusion of value in array" do
@@ -368,9 +368,9 @@ class EnumTest < ActiveRecord::TestCase
     end
     klass.delete_all
     invalid_book = klass.new(status: "proposed")
-    assert_not invalid_book.valid?
+    assert_not_predicate invalid_book, :valid?
     valid_book = klass.new(status: "written")
-    assert valid_book.valid?
+    assert_predicate valid_book, :valid?
   end
 
   test "enums are distinct per class" do
@@ -417,10 +417,10 @@ class EnumTest < ActiveRecord::TestCase
     end
 
     book1 = klass.proposed.create!
-    assert book1.proposed?
+    assert_predicate book1, :proposed?
 
     book2 = klass.single.create!
-    assert book2.single?
+    assert_predicate book2, :single?
   end
 
   test "enum with alias_attribute" do
@@ -431,62 +431,62 @@ class EnumTest < ActiveRecord::TestCase
     end
 
     book = klass.proposed.create!
-    assert book.proposed?
+    assert_predicate book, :proposed?
     assert_equal "proposed", book.aliased_status
 
     book = klass.find(book.id)
-    assert book.proposed?
+    assert_predicate book, :proposed?
     assert_equal "proposed", book.aliased_status
   end
 
   test "query state by predicate with prefix" do
-    assert @book.author_visibility_visible?
-    assert_not @book.author_visibility_invisible?
-    assert @book.illustrator_visibility_visible?
-    assert_not @book.illustrator_visibility_invisible?
+    assert_predicate @book, :author_visibility_visible?
+    assert_not_predicate @book, :author_visibility_invisible?
+    assert_predicate @book, :illustrator_visibility_visible?
+    assert_not_predicate @book, :illustrator_visibility_invisible?
   end
 
   test "query state by predicate with custom prefix" do
-    assert @book.in_english?
-    assert_not @book.in_spanish?
-    assert_not @book.in_french?
+    assert_predicate @book, :in_english?
+    assert_not_predicate @book, :in_spanish?
+    assert_not_predicate @book, :in_french?
   end
 
   test "query state by predicate with custom suffix" do
-    assert     @book.medium_to_read?
-    assert_not @book.easy_to_read?
-    assert_not @book.hard_to_read?
+    assert_predicate @book, :medium_to_read?
+    assert_not_predicate @book, :easy_to_read?
+    assert_not_predicate @book, :hard_to_read?
   end
 
   test "enum methods with custom suffix defined" do
-    assert @book.class.respond_to?(:easy_to_read)
-    assert @book.class.respond_to?(:medium_to_read)
-    assert @book.class.respond_to?(:hard_to_read)
+    assert_respond_to @book.class, :easy_to_read
+    assert_respond_to @book.class, :medium_to_read
+    assert_respond_to @book.class, :hard_to_read
 
-    assert @book.respond_to?(:easy_to_read?)
-    assert @book.respond_to?(:medium_to_read?)
-    assert @book.respond_to?(:hard_to_read?)
+    assert_respond_to @book, :easy_to_read?
+    assert_respond_to @book, :medium_to_read?
+    assert_respond_to @book, :hard_to_read?
 
-    assert @book.respond_to?(:easy_to_read!)
-    assert @book.respond_to?(:medium_to_read!)
-    assert @book.respond_to?(:hard_to_read!)
+    assert_respond_to @book, :easy_to_read!
+    assert_respond_to @book, :medium_to_read!
+    assert_respond_to @book, :hard_to_read!
   end
 
   test "update enum attributes with custom suffix" do
     @book.medium_to_read!
-    assert_not @book.easy_to_read?
-    assert     @book.medium_to_read?
-    assert_not @book.hard_to_read?
+    assert_not_predicate @book, :easy_to_read?
+    assert_predicate @book, :medium_to_read?
+    assert_not_predicate @book, :hard_to_read?
 
     @book.easy_to_read!
-    assert     @book.easy_to_read?
-    assert_not @book.medium_to_read?
-    assert_not @book.hard_to_read?
+    assert_predicate @book, :easy_to_read?
+    assert_not_predicate @book, :medium_to_read?
+    assert_not_predicate @book, :hard_to_read?
 
     @book.hard_to_read!
-    assert_not @book.easy_to_read?
-    assert_not @book.medium_to_read?
-    assert     @book.hard_to_read?
+    assert_not_predicate @book, :easy_to_read?
+    assert_not_predicate @book, :medium_to_read?
+    assert_predicate @book, :hard_to_read?
   end
 
   test "uses default status when no status is provided in fixtures" do
@@ -497,12 +497,12 @@ class EnumTest < ActiveRecord::TestCase
 
   test "uses default value from database on initialization" do
     book = Book.new
-    assert book.proposed?
+    assert_predicate book, :proposed?
   end
 
   test "uses default value from database on initialization when using custom mapping" do
     book = Book.new
-    assert book.hard?
+    assert_predicate book, :hard?
   end
 
   test "data type of Enum type" do
diff --git a/activerecord/test/cases/explain_subscriber_test.rb b/activerecord/test/cases/explain_subscriber_test.rb
index fb698c47cd..82cc891970 100644
--- a/activerecord/test/cases/explain_subscriber_test.rb
+++ b/activerecord/test/cases/explain_subscriber_test.rb
@@ -15,20 +15,20 @@ if ActiveRecord::Base.connection.supports_explain?
 
     def test_collects_nothing_if_the_payload_has_an_exception
       SUBSCRIBER.finish(nil, nil, exception: Exception.new)
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_nothing_for_ignored_payloads
       ActiveRecord::ExplainSubscriber::IGNORED_PAYLOADS.each do |ip|
         SUBSCRIBER.finish(nil, nil, name: ip)
       end
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_nothing_if_collect_is_false
       ActiveRecord::ExplainRegistry.collect = false
       SUBSCRIBER.finish(nil, nil, name: "SQL", sql: "select 1 from users", binds: [1, 2])
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_pairs_of_queries_and_binds
@@ -42,12 +42,12 @@ if ActiveRecord::Base.connection.supports_explain?
 
     def test_collects_nothing_if_the_statement_is_not_whitelisted
       SUBSCRIBER.finish(nil, nil, name: "SQL", sql: "SHOW max_identifier_length")
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_nothing_if_the_statement_is_only_partially_matched
       SUBSCRIBER.finish(nil, nil, name: "SQL", sql: "select_db yo_mama")
-      assert queries.empty?
+      assert_empty queries
     end
 
     def test_collects_cte_queries
diff --git a/activerecord/test/cases/explain_test.rb b/activerecord/test/cases/explain_test.rb
index 17654027a9..a0e75f4e89 100644
--- a/activerecord/test/cases/explain_test.rb
+++ b/activerecord/test/cases/explain_test.rb
@@ -2,7 +2,6 @@
 
 require "cases/helper"
 require "models/car"
-require "active_support/core_ext/string/strip"
 
 if ActiveRecord::Base.connection.supports_explain?
   class ExplainTest < ActiveRecord::TestCase
@@ -53,7 +52,7 @@ if ActiveRecord::Base.connection.supports_explain?
       queries = sqls.zip(binds)
 
       stub_explain_for_query_plans(["query plan foo\n", "query plan bar\n"]) do
-        expected = <<-SQL.strip_heredoc
+        expected = <<~SQL
           EXPLAIN for: #{sqls[0]} [["wadus", 1]]
           query plan foo
 
diff --git a/activerecord/test/cases/finder_respond_to_test.rb b/activerecord/test/cases/finder_respond_to_test.rb
index 4039af66d0..59af4e6961 100644
--- a/activerecord/test/cases/finder_respond_to_test.rb
+++ b/activerecord/test/cases/finder_respond_to_test.rb
@@ -8,7 +8,7 @@ class FinderRespondToTest < ActiveRecord::TestCase
 
   def test_should_preserve_normal_respond_to_behaviour_on_base
     assert_respond_to ActiveRecord::Base, :new
-    assert !ActiveRecord::Base.respond_to?(:find_by_something)
+    assert_not_respond_to ActiveRecord::Base, :find_by_something
   end
 
   def test_should_preserve_normal_respond_to_behaviour_and_respond_to_newly_added_method
@@ -43,14 +43,14 @@ class FinderRespondToTest < ActiveRecord::TestCase
   end
 
   def test_should_not_respond_to_find_by_one_missing_attribute
-    assert !Topic.respond_to?(:find_by_undertitle)
+    assert_not_respond_to Topic, :find_by_undertitle
   end
 
   def test_should_not_respond_to_find_by_invalid_method_syntax
-    assert !Topic.respond_to?(:fail_to_find_by_title)
-    assert !Topic.respond_to?(:find_by_title?)
-    assert !Topic.respond_to?(:fail_to_find_or_create_by_title)
-    assert !Topic.respond_to?(:find_or_create_by_title?)
+    assert_not_respond_to Topic, :fail_to_find_by_title
+    assert_not_respond_to Topic, :find_by_title?
+    assert_not_respond_to Topic, :fail_to_find_or_create_by_title
+    assert_not_respond_to Topic, :find_or_create_by_title?
   end
 
   private
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index 4769ffd64d..ebddf81449 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -648,13 +648,13 @@ class FinderTest < ActiveRecord::TestCase
   def test_last_with_integer_and_order_should_use_sql_limit
     relation = Topic.order("title")
     assert_queries(1) { relation.last(5) }
-    assert !relation.loaded?
+    assert_not_predicate relation, :loaded?
   end
 
   def test_last_with_integer_and_reorder_should_use_sql_limit
     relation = Topic.reorder("title")
     assert_queries(1) { relation.last(5) }
-    assert !relation.loaded?
+    assert_not_predicate relation, :loaded?
   end
 
   def test_last_on_loaded_relation_should_not_use_sql
@@ -812,6 +812,15 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal [1, 2, 6, 7, 8], Comment.where(id: [1..2, 6..8]).to_a.map(&:id).sort
   end
 
+  def test_find_on_hash_conditions_with_open_ended_range
+    assert_equal [1, 2, 3], Comment.where(id: Float::INFINITY..3).to_a.map(&:id).sort
+  end
+
+  def test_find_on_hash_conditions_with_numeric_range_for_string
+    topic = Topic.create!(title: "12 Factor App")
+    assert_equal [topic], Topic.where(title: 10..2).to_a
+  end
+
   def test_find_on_multiple_hash_conditions
     assert Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: false).find(1)
     assert_raise(ActiveRecord::RecordNotFound) { Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: true).find(1) }
@@ -868,6 +877,25 @@ class FinderTest < ActiveRecord::TestCase
     assert_equal customers(:david), found_customer
   end
 
+  def test_hash_condition_find_with_aggregate_having_three_mappings_array
+    david_address = customers(:david).address
+    zaphod_address = customers(:zaphod).address
+    barney_address = customers(:barney).address
+    assert_kind_of Address, david_address
+    assert_kind_of Address, zaphod_address
+    found_customers = Customer.where(address: [david_address, zaphod_address, barney_address])
+    assert_equal [customers(:david), customers(:zaphod), customers(:barney)], found_customers.sort_by(&:id)
+  end
+
+  def test_hash_condition_find_with_aggregate_having_one_mapping_array
+    david_balance = customers(:david).balance
+    zaphod_balance = customers(:zaphod).balance
+    assert_kind_of Money, david_balance
+    assert_kind_of Money, zaphod_balance
+    found_customers = Customer.where(balance: [david_balance, zaphod_balance])
+    assert_equal [customers(:david), customers(:zaphod)], found_customers.sort_by(&:id)
+  end
+
   def test_hash_condition_find_with_aggregate_attribute_having_same_name_as_field_and_key_value_being_aggregate
     gps_location = customers(:david).gps_location
     assert_kind_of GpsLocation, gps_location
diff --git a/activerecord/test/cases/fixtures_test.rb b/activerecord/test/cases/fixtures_test.rb
index 8e8a49af8e..184b750161 100644
--- a/activerecord/test/cases/fixtures_test.rb
+++ b/activerecord/test/cases/fixtures_test.rb
@@ -79,6 +79,151 @@ class FixturesTest < ActiveRecord::TestCase
         ActiveSupport::Notifications.unsubscribe(subscription)
       end
     end
+
+    def test_bulk_insert_multiple_table_with_a_multi_statement_query
+      subscriber = InsertQuerySubscriber.new
+      subscription = ActiveSupport::Notifications.subscribe("sql.active_record", subscriber)
+
+      create_fixtures("bulbs", "authors", "computers")
+
+      expected_sql = <<~EOS.chop
+        INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("bulbs")} .*
+        INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("authors")} .*
+        INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("computers")} .*
+      EOS
+      assert_equal 1, subscriber.events.size
+      assert_match(/#{expected_sql}/, subscriber.events.first)
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+
+    def test_bulk_insert_with_a_multi_statement_query_raises_an_exception_when_any_insert_fails
+      require "models/aircraft"
+
+      assert_equal false, Aircraft.columns_hash["wheels_count"].null
+      fixtures = {
+        "aircraft" => [
+          { "name" => "working_aircrafts", "wheels_count" => 2 },
+          { "name" => "broken_aircrafts", "wheels_count" => nil },
+        ]
+      }
+
+      assert_no_difference "Aircraft.count" do
+        assert_raises(ActiveRecord::NotNullViolation) do
+          ActiveRecord::Base.connection.insert_fixtures_set(fixtures)
+        end
+      end
+    end
+  end
+
+  if current_adapter?(:Mysql2Adapter)
+    def test_insert_fixtures_set_raises_an_error_when_max_allowed_packet_is_smaller_than_fixtures_set_size
+      conn = ActiveRecord::Base.connection
+      mysql_margin = 2
+      packet_size = 1024
+      bytes_needed_to_have_a_1024_bytes_fixture = 858
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * bytes_needed_to_have_a_1024_bytes_fixture] },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size - mysql_margin)
+
+      error = assert_raises(ActiveRecord::ActiveRecordError) { conn.insert_fixtures_set(fixtures) }
+      assert_match(/Fixtures set is too large #{packet_size}\./, error.message)
+    end
+
+    def test_insert_fixture_set_when_max_allowed_packet_is_bigger_than_fixtures_set_size
+      conn = ActiveRecord::Base.connection
+      packet_size = 1024
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * 51] },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size)
+
+      assert_difference "TrafficLight.count" do
+        conn.insert_fixtures_set(fixtures)
+      end
+    end
+
+    def test_insert_fixtures_set_split_the_total_sql_into_two_chunks_smaller_than_max_allowed_packet
+      subscriber = InsertQuerySubscriber.new
+      subscription = ActiveSupport::Notifications.subscribe("sql.active_record", subscriber)
+      conn = ActiveRecord::Base.connection
+      packet_size = 1024
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * 450] },
+        ],
+        "comments" => [
+          { "post_id" => 1, "body" => "a" * 450 },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size)
+
+      conn.insert_fixtures_set(fixtures)
+      assert_equal 2, subscriber.events.size
+      assert_operator subscriber.events.first.bytesize, :<, packet_size
+      assert_operator subscriber.events.second.bytesize, :<, packet_size
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+
+    def test_insert_fixtures_set_concat_total_sql_into_a_single_packet_smaller_than_max_allowed_packet
+      subscriber = InsertQuerySubscriber.new
+      subscription = ActiveSupport::Notifications.subscribe("sql.active_record", subscriber)
+      conn = ActiveRecord::Base.connection
+      packet_size = 1024
+      fixtures = {
+        "traffic_lights" => [
+          { "location" => "US", "state" => ["NY"], "long_state" => ["a" * 200] },
+        ],
+        "comments" => [
+          { "post_id" => 1, "body" => "a" * 200 },
+        ]
+      }
+
+      conn.stubs(:max_allowed_packet).returns(packet_size)
+
+      assert_difference ["TrafficLight.count", "Comment.count"], +1 do
+        conn.insert_fixtures_set(fixtures)
+      end
+      assert_equal 1, subscriber.events.size
+    ensure
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+  end
+
+  def test_auto_value_on_primary_key
+    fixtures = [
+      { "name" => "first", "wheels_count" => 2 },
+      { "name" => "second", "wheels_count" => 3 }
+    ]
+    conn = ActiveRecord::Base.connection
+    assert_nothing_raised do
+      conn.insert_fixtures_set({ "aircraft" => fixtures }, ["aircraft"])
+    end
+    result = conn.select_all("SELECT name, wheels_count FROM aircraft ORDER BY id")
+    assert_equal fixtures, result.to_a
+  end
+
+  def test_deprecated_insert_fixtures
+    fixtures = [
+      { "name" => "first", "wheels_count" => 2 },
+      { "name" => "second", "wheels_count" => 3 }
+    ]
+    conn = ActiveRecord::Base.connection
+    conn.delete("DELETE FROM aircraft")
+    assert_deprecated do
+      conn.insert_fixtures(fixtures, "aircraft")
+    end
+    result = conn.select_all("SELECT name, wheels_count FROM aircraft ORDER BY id")
+    assert_equal fixtures, result.to_a
   end
 
   def test_broken_yaml_exception
@@ -248,7 +393,7 @@ class FixturesTest < ActiveRecord::TestCase
     nonexistent_fixture_path = FIXTURES_ROOT + "/imnothere"
 
     # sanity check to make sure that this file never exists
-    assert Dir[nonexistent_fixture_path + "*"].empty?
+    assert_empty Dir[nonexistent_fixture_path + "*"]
 
     assert_raise(Errno::ENOENT) do
       ActiveRecord::FixtureSet.new(Account.connection, "companies", Company, nonexistent_fixture_path)
@@ -998,10 +1143,10 @@ class FoxyFixturesTest < ActiveRecord::TestCase
   end
 
   def test_resolves_enums
-    assert books(:awdr).published?
-    assert books(:awdr).read?
-    assert books(:rfr).proposed?
-    assert books(:ddd).published?
+    assert_predicate books(:awdr), :published?
+    assert_predicate books(:awdr), :read?
+    assert_predicate books(:rfr), :proposed?
+    assert_predicate books(:ddd), :published?
   end
 end
 
@@ -1041,7 +1186,7 @@ class CustomNameForFixtureOrModelTest < ActiveRecord::TestCase
   end
 
   def test_table_name_is_defined_in_the_model
-    assert_equal "randomly_named_table2", ActiveRecord::FixtureSet::all_loaded_fixtures["admin/randomly_named_a9"].table_name
+    assert_equal "randomly_named_table2", ActiveRecord::FixtureSet.all_loaded_fixtures["admin/randomly_named_a9"].table_name
     assert_equal "randomly_named_table2", Admin::ClassNameThatDoesNotFollowCONVENTIONS1.table_name
   end
 end
diff --git a/activerecord/test/cases/habtm_destroy_order_test.rb b/activerecord/test/cases/habtm_destroy_order_test.rb
index 5e503272e1..b15e1b48c4 100644
--- a/activerecord/test/cases/habtm_destroy_order_test.rb
+++ b/activerecord/test/cases/habtm_destroy_order_test.rb
@@ -15,7 +15,7 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
         sicp.destroy
       end
     end
-    assert !sicp.destroyed?
+    assert_not_predicate sicp, :destroyed?
   end
 
   test "should not raise error if have foreign key in the join table" do
@@ -42,7 +42,7 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
       ben.lessons << sicp
       ben.save!
       ben.destroy
-      assert !ben.reload.lessons.empty?
+      assert_not_empty ben.reload.lessons
     ensure
       # get rid of it so Student is still like it was
       Student.reset_callbacks(:destroy)
@@ -58,6 +58,6 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
     assert_raises LessonError do
       sicp.destroy
     end
-    assert !sicp.reload.students.empty?
+    assert_not_empty sicp.reload.students
   end
 end
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index ff4385c8b4..e3ca79af99 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -130,46 +130,46 @@ class InheritanceTest < ActiveRecord::TestCase
   end
 
   def test_descends_from_active_record
-    assert !ActiveRecord::Base.descends_from_active_record?
+    assert_not_predicate ActiveRecord::Base, :descends_from_active_record?
 
     # Abstract subclass of AR::Base.
-    assert LoosePerson.descends_from_active_record?
+    assert_predicate LoosePerson, :descends_from_active_record?
 
     # Concrete subclass of an abstract class.
-    assert LooseDescendant.descends_from_active_record?
+    assert_predicate LooseDescendant, :descends_from_active_record?
 
     # Concrete subclass of AR::Base.
-    assert TightPerson.descends_from_active_record?
+    assert_predicate TightPerson, :descends_from_active_record?
 
     # Concrete subclass of a concrete class but has no type column.
-    assert TightDescendant.descends_from_active_record?
+    assert_predicate TightDescendant, :descends_from_active_record?
 
     # Concrete subclass of AR::Base.
-    assert Post.descends_from_active_record?
+    assert_predicate Post, :descends_from_active_record?
 
     # Concrete subclasses of a concrete class which has a type column.
-    assert !StiPost.descends_from_active_record?
-    assert !SubStiPost.descends_from_active_record?
+    assert_not_predicate StiPost, :descends_from_active_record?
+    assert_not_predicate SubStiPost, :descends_from_active_record?
 
     # Abstract subclass of a concrete class which has a type column.
     # This is pathological, as you'll never have Sub < Abstract < Concrete.
-    assert !AbstractStiPost.descends_from_active_record?
+    assert_not_predicate AbstractStiPost, :descends_from_active_record?
 
     # Concrete subclass of an abstract class which has a type column.
-    assert !SubAbstractStiPost.descends_from_active_record?
+    assert_not_predicate SubAbstractStiPost, :descends_from_active_record?
   end
 
   def test_company_descends_from_active_record
-    assert !ActiveRecord::Base.descends_from_active_record?
+    assert_not_predicate ActiveRecord::Base, :descends_from_active_record?
     assert AbstractCompany.descends_from_active_record?, "AbstractCompany should descend from ActiveRecord::Base"
     assert Company.descends_from_active_record?, "Company should descend from ActiveRecord::Base"
     assert !Class.new(Company).descends_from_active_record?, "Company subclass should not descend from ActiveRecord::Base"
   end
 
   def test_abstract_class
-    assert !ActiveRecord::Base.abstract_class?
-    assert LoosePerson.abstract_class?
-    assert !LooseDescendant.abstract_class?
+    assert_not_predicate ActiveRecord::Base, :abstract_class?
+    assert_predicate LoosePerson, :abstract_class?
+    assert_not_predicate LooseDescendant, :abstract_class?
   end
 
   def test_inheritance_base_class
diff --git a/activerecord/test/cases/json_serialization_test.rb b/activerecord/test/cases/json_serialization_test.rb
index 52fe488cd5..82cf281cff 100644
--- a/activerecord/test/cases/json_serialization_test.rb
+++ b/activerecord/test/cases/json_serialization_test.rb
@@ -252,7 +252,7 @@ class DatabaseConnectedJsonEncodingTest < ActiveRecord::TestCase
     def @david.favorite_quote; "Constraints are liberating"; end
     json = @david.to_json(include: :posts, methods: :favorite_quote)
 
-    assert !@david.posts.first.respond_to?(:favorite_quote)
+    assert_not_respond_to @david.posts.first, :favorite_quote
     assert_match %r{"favorite_quote":"Constraints are liberating"}, json
     assert_equal 1, %r{"favorite_quote":}.match(json).size
   end
diff --git a/activerecord/test/cases/json_shared_test_cases.rb b/activerecord/test/cases/json_shared_test_cases.rb
index b0c0f2c283..9b79803503 100644
--- a/activerecord/test/cases/json_shared_test_cases.rb
+++ b/activerecord/test/cases/json_shared_test_cases.rb
@@ -26,7 +26,7 @@ module JSONSharedTestCases
     assert_type_match column_type, column.sql_type
 
     type = klass.type_for_attribute("payload")
-    assert_not type.binary?
+    assert_not_predicate type, :binary?
   end
 
   def test_change_table_supports_json
@@ -101,7 +101,7 @@ module JSONSharedTestCases
     x = klass.where(payload: nil).first
     assert_nil(x)
 
-    json.update_attributes(payload: nil)
+    json.update(payload: nil)
     x = klass.where(payload: nil).first
     assert_equal(json.reload, x)
   end
@@ -152,42 +152,42 @@ module JSONSharedTestCases
 
   def test_changes_in_place
     json = klass.new
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = { "one" => "two" }
-    assert json.changed?
-    assert json.payload_changed?
+    assert_predicate json, :changed?
+    assert_predicate json, :payload_changed?
 
     json.save!
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload["three"] = "four"
-    assert json.payload_changed?
+    assert_predicate json, :payload_changed?
 
     json.save!
     json.reload
 
     assert_equal({ "one" => "two", "three" => "four" }, json.payload)
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
   end
 
   def test_changes_in_place_ignores_key_order
     json = klass.new
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = { "three" => "four", "one" => "two" }
     json.save!
     json.reload
 
     json.payload = { "three" => "four", "one" => "two" }
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = [{ "three" => "four", "one" => "two" }, { "seven" => "eight", "five" => "six" }]
     json.save!
     json.reload
 
     json.payload = [{ "three" => "four", "one" => "two" }, { "seven" => "eight", "five" => "six" }]
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
   end
 
   def test_changes_in_place_with_ruby_object
@@ -195,10 +195,10 @@ module JSONSharedTestCases
     json = klass.create!(payload: time)
 
     json.reload
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
 
     json.payload = time
-    assert_not json.changed?
+    assert_not_predicate json, :changed?
   end
 
   def test_assigning_string_literal
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index 3701be4b11..02be0aa9e3 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -69,8 +69,8 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_raise(ActiveRecord::StaleObjectError) { s2.destroy }
 
     assert s1.destroy
-    assert s1.frozen?
-    assert s1.destroyed?
+    assert_predicate s1, :frozen?
+    assert_predicate s1, :destroyed?
     assert_raises(ActiveRecord::RecordNotFound) { StringKeyObject.find("record1") }
   end
 
@@ -104,8 +104,8 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::StaleObjectError) { p2.destroy }
 
     assert p1.destroy
-    assert p1.frozen?
-    assert p1.destroyed?
+    assert_predicate p1, :frozen?
+    assert_predicate p1, :destroyed?
     assert_raises(ActiveRecord::RecordNotFound) { Person.find(1) }
   end
 
@@ -201,7 +201,7 @@ class OptimisticLockingTest < ActiveRecord::TestCase
       person.first_name = "Douglas Adams"
       person.lock_version = 42
 
-      assert person.lock_version_changed?
+      assert_predicate person, :lock_version_changed?
 
       person.save
     end
@@ -415,7 +415,9 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_equal 1, car.lock_version
 
     previously_car_updated_at = car.updated_at
-    car.wheels.first.update(size: 42)
+    travel(1.day) do
+      car.wheels.first.update(size: 42)
+    end
 
     assert_equal 1, car.reload.wheels_count
     assert_not_equal previously_car_updated_at, car.updated_at
@@ -440,16 +442,16 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_difference "car.wheels.count", -1  do
       car.reload.destroy
     end
-    assert car.destroyed?
+    assert_predicate car, :destroyed?
   end
 
   def test_removing_has_and_belongs_to_many_associations_upon_destroy
     p = RichPerson.create! first_name: "Jon"
     p.treasures.create!
-    assert !p.treasures.empty?
+    assert_not_empty p.treasures
     p.destroy
-    assert p.treasures.empty?
-    assert RichPerson.connection.select_all("SELECT * FROM peoples_treasures WHERE rich_person_id = 1").empty?
+    assert_empty p.treasures
+    assert_empty RichPerson.connection.select_all("SELECT * FROM peoples_treasures WHERE rich_person_id = 1")
   end
 
   def test_yaml_dumping_with_lock_column
@@ -519,7 +521,7 @@ class OptimisticLockingWithSchemaChangeTest < ActiveRecord::TestCase
 
     t1.destroy
 
-    assert t1.destroyed?
+    assert_predicate t1, :destroyed?
   end
 
   def test_destroy_stale_object
@@ -532,7 +534,7 @@ class OptimisticLockingWithSchemaChangeTest < ActiveRecord::TestCase
       stale_object.destroy!
     end
 
-    refute stale_object.destroyed?
+    assert_not_predicate stale_object, :destroyed?
   end
 
   private
diff --git a/activerecord/test/cases/migration/change_schema_test.rb b/activerecord/test/cases/migration/change_schema_test.rb
index 38a906c8f5..1494027182 100644
--- a/activerecord/test/cases/migration/change_schema_test.rb
+++ b/activerecord/test/cases/migration/change_schema_test.rb
@@ -84,7 +84,7 @@ module ActiveRecord
           columns = connection.columns(:testings)
           array_column = columns.detect { |c| c.name == "foo" }
 
-          assert array_column.array?
+          assert_predicate array_column, :array?
         end
 
         def test_create_table_with_array_column
@@ -95,7 +95,7 @@ module ActiveRecord
           columns = connection.columns(:testings)
           array_column = columns.detect { |c| c.name == "foo" }
 
-          assert array_column.array?
+          assert_predicate array_column, :array?
         end
       end
 
diff --git a/activerecord/test/cases/migration/columns_test.rb b/activerecord/test/cases/migration/columns_test.rb
index 8ca20b6172..cedd9c44e3 100644
--- a/activerecord/test/cases/migration/columns_test.rb
+++ b/activerecord/test/cases/migration/columns_test.rb
@@ -67,7 +67,7 @@ module ActiveRecord
       if current_adapter?(:Mysql2Adapter)
         def test_mysql_rename_column_preserves_auto_increment
           rename_column "test_models", "id", "id_test"
-          assert connection.columns("test_models").find { |c| c.name == "id_test" }.auto_increment?
+          assert_predicate connection.columns("test_models").find { |c| c.name == "id_test" }, :auto_increment?
           TestModel.reset_column_information
         ensure
           rename_column "test_models", "id_test", "id"
@@ -223,31 +223,31 @@ module ActiveRecord
 
       def test_change_column_with_nil_default
         add_column "test_models", "contributor", :boolean, default: true
-        assert TestModel.new.contributor?
+        assert_predicate TestModel.new, :contributor?
 
         change_column "test_models", "contributor", :boolean, default: nil
         TestModel.reset_column_information
-        assert_not TestModel.new.contributor?
+        assert_not_predicate TestModel.new, :contributor?
         assert_nil TestModel.new.contributor
       end
 
       def test_change_column_to_drop_default_with_null_false
         add_column "test_models", "contributor", :boolean, default: true, null: false
-        assert TestModel.new.contributor?
+        assert_predicate TestModel.new, :contributor?
 
         change_column "test_models", "contributor", :boolean, default: nil, null: false
         TestModel.reset_column_information
-        assert_not TestModel.new.contributor?
+        assert_not_predicate TestModel.new, :contributor?
         assert_nil TestModel.new.contributor
       end
 
       def test_change_column_with_new_default
         add_column "test_models", "administrator", :boolean, default: true
-        assert TestModel.new.administrator?
+        assert_predicate TestModel.new, :administrator?
 
         change_column "test_models", "administrator", :boolean, default: false
         TestModel.reset_column_information
-        assert_not TestModel.new.administrator?
+        assert_not_predicate TestModel.new, :administrator?
       end
 
       def test_change_column_with_custom_index_name
diff --git a/activerecord/test/cases/migration/command_recorder_test.rb b/activerecord/test/cases/migration/command_recorder_test.rb
index 58bc558619..3a11bb081b 100644
--- a/activerecord/test/cases/migration/command_recorder_test.rb
+++ b/activerecord/test/cases/migration/command_recorder_test.rb
@@ -14,7 +14,7 @@ module ActiveRecord
         recorder = CommandRecorder.new(Class.new {
           def america; end
         }.new)
-        assert recorder.respond_to?(:america)
+        assert_respond_to recorder, :america
       end
 
       def test_send_calls_super
@@ -27,7 +27,7 @@ module ActiveRecord
         recorder = CommandRecorder.new(Class.new {
           def create_table(name); end
         }.new)
-        assert recorder.respond_to?(:create_table), "respond_to? create_table"
+        assert_respond_to recorder, :create_table
         recorder.send(:create_table, :horses)
         assert_equal [[:create_table, [:horses], nil]], recorder.commands
       end
diff --git a/activerecord/test/cases/migration/compatibility_test.rb b/activerecord/test/cases/migration/compatibility_test.rb
index 26d3b3e29d..69a50674af 100644
--- a/activerecord/test/cases/migration/compatibility_test.rb
+++ b/activerecord/test/cases/migration/compatibility_test.rb
@@ -182,7 +182,7 @@ module LegacyPrimaryKeyTestCases
     assert_legacy_primary_key
 
     legacy_ref = LegacyPrimaryKey.columns_hash["legacy_ref_id"]
-    assert_not legacy_ref.bigint?
+    assert_not_predicate legacy_ref, :bigint?
 
     record1 = LegacyPrimaryKey.create!
     assert_not_nil record1.id
@@ -301,8 +301,8 @@ module LegacyPrimaryKeyTestCases
       @migration.migrate(:up)
 
       legacy_pk = LegacyPrimaryKey.columns_hash["id"]
-      assert legacy_pk.bigint?
-      assert legacy_pk.auto_increment?
+      assert_predicate legacy_pk, :bigint?
+      assert_predicate legacy_pk, :auto_increment?
 
       schema = dump_table_schema "legacy_primary_keys"
       assert_match %r{create_table "legacy_primary_keys", (?!id: :bigint, default: nil)}, schema
@@ -334,7 +334,7 @@ module LegacyPrimaryKeyTestCases
       legacy_pk = LegacyPrimaryKey.columns_hash["id"]
 
       assert_equal :integer, legacy_pk.type
-      assert_not legacy_pk.bigint?
+      assert_not_predicate legacy_pk, :bigint?
       assert_not legacy_pk.null
 
       if current_adapter?(:Mysql2Adapter, :PostgreSQLAdapter)
diff --git a/activerecord/test/cases/migration/create_join_table_test.rb b/activerecord/test/cases/migration/create_join_table_test.rb
index 77d32a24a5..83fb4f9385 100644
--- a/activerecord/test/cases/migration/create_join_table_test.rb
+++ b/activerecord/test/cases/migration/create_join_table_test.rb
@@ -69,7 +69,7 @@ module ActiveRecord
       def test_create_join_table_without_indexes
         connection.create_join_table :artists, :musics
 
-        assert connection.indexes(:artists_musics).blank?
+        assert_predicate connection.indexes(:artists_musics), :blank?
       end
 
       def test_create_join_table_with_index
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index 079be04946..de37215e80 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -235,39 +235,39 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
             assert_equal 1, foreign_keys.size
 
             fk = foreign_keys.first
-            refute fk.validated?
+            assert_not_predicate fk, :validated?
           end
 
           def test_validate_foreign_key_infers_column
             @connection.add_foreign_key :astronauts, :rockets, validate: false
-            refute @connection.foreign_keys("astronauts").first.validated?
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
 
             @connection.validate_foreign_key :astronauts, :rockets
-            assert @connection.foreign_keys("astronauts").first.validated?
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
           end
 
           def test_validate_foreign_key_by_column
             @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", validate: false
-            refute @connection.foreign_keys("astronauts").first.validated?
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
 
             @connection.validate_foreign_key :astronauts, column: "rocket_id"
-            assert @connection.foreign_keys("astronauts").first.validated?
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
           end
 
           def test_validate_foreign_key_by_symbol_column
             @connection.add_foreign_key :astronauts, :rockets, column: :rocket_id, validate: false
-            refute @connection.foreign_keys("astronauts").first.validated?
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
 
             @connection.validate_foreign_key :astronauts, column: :rocket_id
-            assert @connection.foreign_keys("astronauts").first.validated?
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
           end
 
           def test_validate_foreign_key_by_name
             @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk", validate: false
-            refute @connection.foreign_keys("astronauts").first.validated?
+            assert_not_predicate @connection.foreign_keys("astronauts").first, :validated?
 
             @connection.validate_foreign_key :astronauts, name: "fancy_named_fk"
-            assert @connection.foreign_keys("astronauts").first.validated?
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
           end
 
           def test_validate_foreign_non_existing_foreign_key_raises
@@ -280,7 +280,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
             @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk", validate: false
 
             @connection.validate_constraint :astronauts, "fancy_named_fk"
-            assert @connection.foreign_keys("astronauts").first.validated?
+            assert_predicate @connection.foreign_keys("astronauts").first, :validated?
           end
         else
           # Foreign key should still be created, but should not be invalid
@@ -291,7 +291,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
             assert_equal 1, foreign_keys.size
 
             fk = foreign_keys.first
-            assert fk.validated?
+            assert_predicate fk, :validated?
           end
         end
 
diff --git a/activerecord/test/cases/migration/pending_migrations_test.rb b/activerecord/test/cases/migration/pending_migrations_test.rb
index d0066f68be..dedb5ea502 100644
--- a/activerecord/test/cases/migration/pending_migrations_test.rb
+++ b/activerecord/test/cases/migration/pending_migrations_test.rb
@@ -4,37 +4,37 @@ require "cases/helper"
 
 module ActiveRecord
   class Migration
-    class PendingMigrationsTest < ActiveRecord::TestCase
-      def setup
-        super
-        @connection = Minitest::Mock.new
-        @app = Minitest::Mock.new
-        conn = @connection
-        @pending = Class.new(CheckPending) {
-          define_method(:connection) { conn }
-        }.new(@app)
-        @pending.instance_variable_set :@last_check, -1 # Force checking
-      end
+    if current_adapter?(:SQLite3Adapter) && !in_memory_db?
+      class PendingMigrationsTest < ActiveRecord::TestCase
+        setup do
+          file = ActiveRecord::Base.connection.raw_connection.filename
+          @conn = ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:", migrations_paths: MIGRATIONS_ROOT + "/valid"
+          source_db = SQLite3::Database.new file
+          dest_db = ActiveRecord::Base.connection.raw_connection
+          backup = SQLite3::Backup.new(dest_db, "main", source_db, "main")
+          backup.step(-1)
+          backup.finish
+        end
 
-      def teardown
-        assert @connection.verify
-        assert @app.verify
-        super
-      end
+        teardown do
+          @conn.release_connection if @conn
+          ActiveRecord::Base.establish_connection :arunit
+        end
+
+        def test_errors_if_pending
+          ActiveRecord::Base.connection.drop_table "schema_migrations", if_exists: true
 
-      def test_errors_if_pending
-        ActiveRecord::Migrator.stub :needs_migration?, true do
-          assert_raise ActiveRecord::PendingMigrationError do
-            @pending.call(nil)
+          assert_raises ActiveRecord::PendingMigrationError do
+            CheckPending.new(Proc.new {}).call({})
           end
         end
-      end
 
-      def test_checks_if_supported
-        @app.expect :call, nil, [:foo]
+        def test_checks_if_supported
+          ActiveRecord::SchemaMigration.create_table
+          migrator = Base.connection.migration_context
+          capture(:stdout) { migrator.migrate }
 
-        ActiveRecord::Migrator.stub :needs_migration?, false do
-          @pending.call(:foo)
+          assert_nil CheckPending.new(Proc.new {}).call({})
         end
       end
     end
diff --git a/activerecord/test/cases/migration/rename_table_test.rb b/activerecord/test/cases/migration/rename_table_test.rb
index dfce266253..a9deb92585 100644
--- a/activerecord/test/cases/migration/rename_table_test.rb
+++ b/activerecord/test/cases/migration/rename_table_test.rb
@@ -86,9 +86,9 @@ module ActiveRecord
           rename_table :cats, :felines
 
           assert connection.table_exists? :felines
-          refute connection.table_exists? :cats
+          assert_not connection.table_exists? :cats
 
-          primary_key_name = connection.select_values(<<-SQL.strip_heredoc, "SCHEMA")[0]
+          primary_key_name = connection.select_values(<<~SQL, "SCHEMA")[0]
             SELECT c.relname
               FROM pg_class c
               JOIN pg_index i
@@ -107,7 +107,7 @@ module ActiveRecord
           connection.create_table :cats, id: :uuid, default: "uuid_generate_v4()"
           assert_nothing_raised { rename_table :cats, :felines }
           assert connection.table_exists? :felines
-          refute connection.table_exists? :cats
+          assert_not connection.table_exists? :cats
         ensure
           connection.drop_table :cats, if_exists: true
           connection.drop_table :felines, if_exists: true
diff --git a/activerecord/test/cases/migration_test.rb b/activerecord/test/cases/migration_test.rb
index a3ebc8070a..a4b8664a85 100644
--- a/activerecord/test/cases/migration_test.rb
+++ b/activerecord/test/cases/migration_test.rb
@@ -71,6 +71,16 @@ class MigrationTest < ActiveRecord::TestCase
     ActiveRecord::Migration.verbose = @verbose_was
   end
 
+  def test_migrator_migrations_path_is_deprecated
+    assert_deprecated do
+      ActiveRecord::Migrator.migrations_path = "/whatever"
+    end
+  ensure
+    assert_deprecated do
+      ActiveRecord::Migrator.migrations_path = "db/migrate"
+    end
+  end
+
   def test_migration_version_matches_component_version
     assert_equal ActiveRecord::VERSION::STRING.to_f, ActiveRecord::Migration.current_version
   end
@@ -78,20 +88,20 @@ class MigrationTest < ActiveRecord::TestCase
   def test_migrator_versions
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
 
-    ActiveRecord::Migrator.up(migrations_path)
-    assert_equal 3, ActiveRecord::Migrator.current_version
-    assert_equal false, ActiveRecord::Migrator.needs_migration?
+    migrator.up
+    assert_equal 3, migrator.current_version
+    assert_equal false, migrator.needs_migration?
 
-    ActiveRecord::Migrator.down(MIGRATIONS_ROOT + "/valid")
-    assert_equal 0, ActiveRecord::Migrator.current_version
-    assert_equal true, ActiveRecord::Migrator.needs_migration?
+    migrator.down
+    assert_equal 0, migrator.current_version
+    assert_equal true, migrator.needs_migration?
 
     ActiveRecord::SchemaMigration.create!(version: 3)
-    assert_equal true, ActiveRecord::Migrator.needs_migration?
+    assert_equal true, migrator.needs_migration?
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    ActiveRecord::MigrationContext.new(old_path)
   end
 
   def test_migration_detection_without_schema_migration_table
@@ -99,28 +109,31 @@ class MigrationTest < ActiveRecord::TestCase
 
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
 
-    assert_equal true, ActiveRecord::Migrator.needs_migration?
+    assert_equal true, migrator.needs_migration?
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    ActiveRecord::MigrationContext.new(old_path)
   end
 
   def test_any_migrations
     old_path = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = MIGRATIONS_ROOT + "/valid"
+    migrator = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid")
 
-    assert ActiveRecord::Migrator.any_migrations?
+    assert_predicate migrator, :any_migrations?
 
-    ActiveRecord::Migrator.migrations_paths = MIGRATIONS_ROOT + "/empty"
+    migrator_empty = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/empty")
 
-    assert_not ActiveRecord::Migrator.any_migrations?
+    assert_not_predicate migrator_empty, :any_migrations?
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    ActiveRecord::MigrationContext.new(old_path)
   end
 
   def test_migration_version
-    assert_nothing_raised { ActiveRecord::Migrator.run(:up, MIGRATIONS_ROOT + "/version_check", 20131219224947) }
+    migrator = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/version_check")
+    assert_equal 0, migrator.current_version
+    migrator.up(20131219224947)
+    assert_equal 20131219224947, migrator.current_version
   end
 
   def test_create_table_with_force_true_does_not_drop_nonexisting_table
@@ -157,7 +170,7 @@ class MigrationTest < ActiveRecord::TestCase
   def test_add_table_with_decimals
     Person.connection.drop_table :big_numbers rescue nil
 
-    assert !BigNumber.table_exists?
+    assert_not_predicate BigNumber, :table_exists?
     GiveMeBigNumbers.up
     BigNumber.reset_column_information
 
@@ -216,15 +229,16 @@ class MigrationTest < ActiveRecord::TestCase
 
   def test_filtering_migrations
     assert_no_column Person, :last_name
-    assert !Reminder.table_exists?
+    assert_not_predicate Reminder, :table_exists?
 
     name_filter = lambda { |migration| migration.name == "ValidPeopleHaveLastNames" }
-    ActiveRecord::Migrator.up(MIGRATIONS_ROOT + "/valid", &name_filter)
+    migrator = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid")
+    migrator.up(&name_filter)
 
     assert_column Person, :last_name
     assert_raise(ActiveRecord::StatementInvalid) { Reminder.first }
 
-    ActiveRecord::Migrator.down(MIGRATIONS_ROOT + "/valid", &name_filter)
+    migrator.down(&name_filter)
 
     assert_no_column Person, :last_name
     assert_raise(ActiveRecord::StatementInvalid) { Reminder.first }
@@ -382,9 +396,9 @@ class MigrationTest < ActiveRecord::TestCase
     current_env     = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path        = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
 
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator.up
     assert_equal current_env, ActiveRecord::InternalMetadata[:environment]
 
     original_rails_env  = ENV["RAILS_ENV"]
@@ -395,13 +409,13 @@ class MigrationTest < ActiveRecord::TestCase
     refute_equal current_env, new_env
 
     sleep 1 # mysql by default does not store fractional seconds in the database
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator.up
     assert_equal new_env, ActiveRecord::InternalMetadata[:environment]
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    migrator = ActiveRecord::MigrationContext.new(old_path)
     ENV["RAILS_ENV"] = original_rails_env
     ENV["RACK_ENV"]  = original_rack_env
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator.up
   end
 
   def test_internal_metadata_stores_environment_when_other_data_exists
@@ -411,14 +425,15 @@ class MigrationTest < ActiveRecord::TestCase
     current_env     = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
     migrations_path = MIGRATIONS_ROOT + "/valid"
     old_path        = ActiveRecord::Migrator.migrations_paths
-    ActiveRecord::Migrator.migrations_paths = migrations_path
 
     current_env = ActiveRecord::ConnectionHandling::DEFAULT_ENV.call
-    ActiveRecord::Migrator.up(migrations_path)
+    migrator = ActiveRecord::MigrationContext.new(migrations_path)
+    migrator.up
     assert_equal current_env, ActiveRecord::InternalMetadata[:environment]
     assert_equal "bar", ActiveRecord::InternalMetadata[:foo]
   ensure
-    ActiveRecord::Migrator.migrations_paths = old_path
+    migrator = ActiveRecord::MigrationContext.new(old_path)
+    migrator.up
   end
 
   def test_proper_table_name_on_migration
@@ -450,7 +465,7 @@ class MigrationTest < ActiveRecord::TestCase
   end
 
   def test_rename_table_with_prefix_and_suffix
-    assert !Thing.table_exists?
+    assert_not_predicate Thing, :table_exists?
     ActiveRecord::Base.table_name_prefix = "p_"
     ActiveRecord::Base.table_name_suffix = "_s"
     Thing.reset_table_name
@@ -471,7 +486,7 @@ class MigrationTest < ActiveRecord::TestCase
   end
 
   def test_add_drop_table_with_prefix_and_suffix
-    assert !Reminder.table_exists?
+    assert_not_predicate Reminder, :table_exists?
     ActiveRecord::Base.table_name_prefix = "prefix_"
     ActiveRecord::Base.table_name_suffix = "_suffix"
     Reminder.reset_table_name
@@ -866,7 +881,7 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
       classname = ActiveRecord::Base.connection.class.name[/[^:]*$/]
       expected_query_count = {
         "Mysql2Adapter"     => 3, # one query for columns, one query for primary key, one query to do the bulk change
-        "PostgreSQLAdapter" => 2, # one query for columns, one for bulk change
+        "PostgreSQLAdapter" => 3, # one query for columns, one for bulk change, one for comment
       }.fetch(classname) {
         raise "need an expected query count for #{classname}"
       }
@@ -874,12 +889,13 @@ if ActiveRecord::Base.connection.supports_bulk_alter?
       assert_queries(expected_query_count, ignore_none: true) do
         with_bulk_change_table do |t|
           t.change :name, :string, default: "NONAME"
-          t.change :birthdate, :datetime
+          t.change :birthdate, :datetime, comment: "This is a comment"
         end
       end
 
       assert_equal "NONAME", column(:name).default
       assert_equal :datetime, column(:birthdate).type
+      assert_equal "This is a comment", column(:birthdate).comment
     end
 
     private
@@ -939,7 +955,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
     files_count = Dir[@migrations_path + "/*.rb"].length
     copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy")
     assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-    assert copied.empty?
+    assert_empty copied
   ensure
     clear
   end
@@ -980,7 +996,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
       files_count = Dir[@migrations_path + "/*.rb"].length
       copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy_with_timestamps")
       assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-      assert copied.empty?
+      assert_empty copied
     end
   ensure
     clear
@@ -1022,7 +1038,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
       files_count = Dir[@migrations_path + "/*.rb"].length
       copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/to_copy_with_timestamps")
       assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-      assert copied.empty?
+      assert_empty copied
     end
   ensure
     clear
@@ -1043,7 +1059,7 @@ class CopyMigrationsTest < ActiveRecord::TestCase
     files_count = Dir[@migrations_path + "/*.rb"].length
     copied = ActiveRecord::Migration.copy(@migrations_path, bukkits: MIGRATIONS_ROOT + "/magic")
     assert_equal files_count, Dir[@migrations_path + "/*.rb"].length
-    assert copied.empty?
+    assert_empty copied
   ensure
     clear
   end
diff --git a/activerecord/test/cases/migrator_test.rb b/activerecord/test/cases/migrator_test.rb
index 1047ba1367..873455cf67 100644
--- a/activerecord/test/cases/migrator_test.rb
+++ b/activerecord/test/cases/migrator_test.rb
@@ -89,7 +89,7 @@ class MigratorTest < ActiveRecord::TestCase
   end
 
   def test_finds_migrations
-    migrations = ActiveRecord::Migrator.migrations(MIGRATIONS_ROOT + "/valid")
+    migrations = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid").migrations
 
     [[1, "ValidPeopleHaveLastNames"], [2, "WeNeedReminders"], [3, "InnocentJointable"]].each_with_index do |pair, i|
       assert_equal migrations[i].version, pair.first
@@ -98,7 +98,8 @@ class MigratorTest < ActiveRecord::TestCase
   end
 
   def test_finds_migrations_in_subdirectories
-    migrations = ActiveRecord::Migrator.migrations(MIGRATIONS_ROOT + "/valid_with_subdirectories")
+    migrations = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/valid_with_subdirectories").migrations
+
 
     [[1, "ValidPeopleHaveLastNames"], [2, "WeNeedReminders"], [3, "InnocentJointable"]].each_with_index do |pair, i|
       assert_equal migrations[i].version, pair.first
@@ -108,7 +109,7 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_finds_migrations_from_two_directories
     directories = [MIGRATIONS_ROOT + "/valid_with_timestamps", MIGRATIONS_ROOT + "/to_copy_with_timestamps"]
-    migrations = ActiveRecord::Migrator.migrations directories
+    migrations = ActiveRecord::MigrationContext.new(directories).migrations
 
     [[20090101010101, "PeopleHaveHobbies"],
      [20090101010202, "PeopleHaveDescriptions"],
@@ -121,14 +122,14 @@ class MigratorTest < ActiveRecord::TestCase
   end
 
   def test_finds_migrations_in_numbered_directory
-    migrations = ActiveRecord::Migrator.migrations [MIGRATIONS_ROOT + "/10_urban"]
+    migrations = ActiveRecord::MigrationContext.new(MIGRATIONS_ROOT + "/10_urban").migrations
     assert_equal 9, migrations[0].version
     assert_equal "AddExpressions", migrations[0].name
   end
 
   def test_relative_migrations
     list = Dir.chdir(MIGRATIONS_ROOT) do
-      ActiveRecord::Migrator.migrations("valid")
+      ActiveRecord::MigrationContext.new("valid").migrations
     end
 
     migration_proxy = list.find { |item|
@@ -157,7 +158,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["up",   "002", "We need reminders"],
       ["down", "003", "Innocent jointable"],
       ["up",   "010", "********** NO FILE **********"],
-    ], ActiveRecord::Migrator.migrations_status(path)
+    ], ActiveRecord::MigrationContext.new(path).migrations_status
   end
 
   def test_migrations_status_in_subdirectories
@@ -171,7 +172,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["up",   "002", "We need reminders"],
       ["down", "003", "Innocent jointable"],
       ["up",   "010", "********** NO FILE **********"],
-    ], ActiveRecord::Migrator.migrations_status(path)
+    ], ActiveRecord::MigrationContext.new(path).migrations_status
   end
 
   def test_migrations_status_with_schema_define_in_subdirectories
@@ -186,7 +187,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["up", "001", "Valid people have last names"],
       ["up", "002", "We need reminders"],
       ["up", "003", "Innocent jointable"],
-    ], ActiveRecord::Migrator.migrations_status(path)
+    ], ActiveRecord::MigrationContext.new(path).migrations_status
   ensure
     ActiveRecord::Migrator.migrations_paths = prev_paths
   end
@@ -204,7 +205,7 @@ class MigratorTest < ActiveRecord::TestCase
       ["down", "20100201010101", "Valid with timestamps we need reminders"],
       ["down", "20100301010101", "Valid with timestamps innocent jointable"],
       ["up",   "20160528010101", "********** NO FILE **********"],
-    ], ActiveRecord::Migrator.migrations_status(paths)
+    ], ActiveRecord::MigrationContext.new(paths).migrations_status
   end
 
   def test_migrator_interleaved_migrations
@@ -232,25 +233,28 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_up_calls_up
     migrations = [Sensor.new(nil, 0), Sensor.new(nil, 1), Sensor.new(nil, 2)]
-    ActiveRecord::Migrator.new(:up, migrations).migrate
+    migrator = ActiveRecord::Migrator.new(:up, migrations)
+    migrator.migrate
     assert migrations.all?(&:went_up)
     assert migrations.all? { |m| !m.went_down }
-    assert_equal 2, ActiveRecord::Migrator.current_version
+    assert_equal 2, migrator.current_version
   end
 
   def test_down_calls_down
     test_up_calls_up
 
     migrations = [Sensor.new(nil, 0), Sensor.new(nil, 1), Sensor.new(nil, 2)]
-    ActiveRecord::Migrator.new(:down, migrations).migrate
+    migrator = ActiveRecord::Migrator.new(:down, migrations)
+    migrator.migrate
     assert migrations.all? { |m| !m.went_up }
     assert migrations.all?(&:went_down)
-    assert_equal 0, ActiveRecord::Migrator.current_version
+    assert_equal 0, migrator.current_version
   end
 
   def test_current_version
     ActiveRecord::SchemaMigration.create!(version: "1000")
-    assert_equal 1000, ActiveRecord::Migrator.current_version
+    migrator = ActiveRecord::MigrationContext.new("db/migrate")
+    assert_equal 1000, migrator.current_version
   end
 
   def test_migrator_one_up
@@ -289,33 +293,36 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_migrator_double_up
     calls, migrations = sensors(3)
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    migrator = ActiveRecord::Migrator.new(:up, migrations, 1)
+    assert_equal(0, migrator.current_version)
 
-    ActiveRecord::Migrator.new(:up, migrations, 1).migrate
+    migrator.migrate
     assert_equal [[:up, 1]], calls
     calls.clear
 
-    ActiveRecord::Migrator.new(:up, migrations, 1).migrate
+    migrator.migrate
     assert_equal [], calls
   end
 
   def test_migrator_double_down
     calls, migrations = sensors(3)
+    migrator = ActiveRecord::Migrator.new(:up, migrations, 1)
 
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    assert_equal 0, migrator.current_version
 
-    ActiveRecord::Migrator.new(:up, migrations, 1).run
+    migrator.run
     assert_equal [[:up, 1]], calls
     calls.clear
 
-    ActiveRecord::Migrator.new(:down, migrations, 1).run
+    migrator = ActiveRecord::Migrator.new(:down, migrations, 1)
+    migrator.run
     assert_equal [[:down, 1]], calls
     calls.clear
 
-    ActiveRecord::Migrator.new(:down, migrations, 1).run
+    migrator.run
     assert_equal [], calls
 
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    assert_equal 0, migrator.current_version
   end
 
   def test_migrator_verbosity
@@ -361,78 +368,85 @@ class MigratorTest < ActiveRecord::TestCase
 
   def test_migrator_going_down_due_to_version_target
     calls, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    migrator.up("valid", 1)
+    migrator.up(1)
     assert_equal [[:up, 1]], calls
     calls.clear
 
-    migrator.migrate("valid", 0)
+    migrator.migrate(0)
     assert_equal [[:down, 1]], calls
     calls.clear
 
-    migrator.migrate("valid")
+    migrator.migrate
     assert_equal [[:up, 1], [:up, 2], [:up, 3]], calls
   end
 
   def test_migrator_output_when_running_multiple_migrations
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    result = migrator.migrate("valid")
+    result = migrator.migrate
     assert_equal(3, result.count)
 
     # Nothing migrated from duplicate run
-    result = migrator.migrate("valid")
+    result = migrator.migrate
     assert_equal(0, result.count)
 
-    result = migrator.rollback("valid")
+    result = migrator.rollback
     assert_equal(1, result.count)
   end
 
   def test_migrator_output_when_running_single_migration
     _, migrator = migrator_class(1)
-    result = migrator.run(:up, "valid", 1)
+    migrator = migrator.new("valid")
+
+    result = migrator.run(:up, 1)
 
     assert_equal(1, result.version)
   end
 
   def test_migrator_rollback
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    migrator.migrate("valid")
-    assert_equal(3, ActiveRecord::Migrator.current_version)
+    migrator.migrate
+    assert_equal(3, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(2, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(2, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(1, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(1, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(0, migrator.current_version)
 
-    migrator.rollback("valid")
-    assert_equal(0, ActiveRecord::Migrator.current_version)
+    migrator.rollback
+    assert_equal(0, migrator.current_version)
   end
 
   def test_migrator_db_has_no_schema_migrations_table
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
     ActiveRecord::Base.connection.drop_table "schema_migrations", if_exists: true
     assert_not ActiveRecord::Base.connection.table_exists?("schema_migrations")
-    migrator.migrate("valid", 1)
+    migrator.migrate(1)
     assert ActiveRecord::Base.connection.table_exists?("schema_migrations")
   end
 
   def test_migrator_forward
     _, migrator = migrator_class(3)
-    migrator.migrate("/valid", 1)
-    assert_equal(1, ActiveRecord::Migrator.current_version)
+    migrator = migrator.new("/valid")
+    migrator.migrate(1)
+    assert_equal(1, migrator.current_version)
 
-    migrator.forward("/valid", 2)
-    assert_equal(3, ActiveRecord::Migrator.current_version)
+    migrator.forward(2)
+    assert_equal(3, migrator.current_version)
 
-    migrator.forward("/valid")
-    assert_equal(3, ActiveRecord::Migrator.current_version)
+    migrator.forward
+    assert_equal(3, migrator.current_version)
   end
 
   def test_only_loads_pending_migrations
@@ -440,25 +454,27 @@ class MigratorTest < ActiveRecord::TestCase
     ActiveRecord::SchemaMigration.create!(version: "1")
 
     calls, migrator = migrator_class(3)
-    migrator.migrate("valid", nil)
+    migrator = migrator.new("valid")
+    migrator.migrate
 
     assert_equal [[:up, 2], [:up, 3]], calls
   end
 
   def test_get_all_versions
     _, migrator = migrator_class(3)
+    migrator = migrator.new("valid")
 
-    migrator.migrate("valid")
-    assert_equal([1, 2, 3], ActiveRecord::Migrator.get_all_versions)
+    migrator.migrate
+    assert_equal([1, 2, 3], migrator.get_all_versions)
 
-    migrator.rollback("valid")
-    assert_equal([1, 2], ActiveRecord::Migrator.get_all_versions)
+    migrator.rollback
+    assert_equal([1, 2], migrator.get_all_versions)
 
-    migrator.rollback("valid")
-    assert_equal([1], ActiveRecord::Migrator.get_all_versions)
+    migrator.rollback
+    assert_equal([1], migrator.get_all_versions)
 
-    migrator.rollback("valid")
-    assert_equal([], ActiveRecord::Migrator.get_all_versions)
+    migrator.rollback
+    assert_equal([], migrator.get_all_versions)
   end
 
   private
@@ -483,11 +499,11 @@ class MigratorTest < ActiveRecord::TestCase
     def migrator_class(count)
       calls, migrations = sensors(count)
 
-      migrator = Class.new(ActiveRecord::Migrator).extend(Module.new {
-        define_method(:migrations) { |paths|
+      migrator = Class.new(ActiveRecord::MigrationContext) {
+        define_method(:migrations) { |*|
           migrations
         }
-      })
+      }
       [calls, migrator]
     end
 end
diff --git a/activerecord/test/cases/multiparameter_attributes_test.rb b/activerecord/test/cases/multiparameter_attributes_test.rb
index 59be4dc5a8..a24b173cf5 100644
--- a/activerecord/test/cases/multiparameter_attributes_test.rb
+++ b/activerecord/test/cases/multiparameter_attributes_test.rb
@@ -227,7 +227,7 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
       topic = Topic.find(1)
       topic.attributes = attributes
       assert_equal Time.local(2004, 6, 24, 16, 24, 0), topic.written_on
-      assert_equal false, topic.written_on.respond_to?(:time_zone)
+      assert_not_respond_to topic.written_on, :time_zone
     end
   end
 
@@ -242,7 +242,7 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
       topic = Topic.find(1)
       topic.attributes = attributes
       assert_equal Time.utc(2004, 6, 24, 16, 24, 0), topic.written_on
-      assert_equal false, topic.written_on.respond_to?(:time_zone)
+      assert_not_respond_to topic.written_on, :time_zone
     end
   ensure
     Topic.skip_time_zone_conversion_for_attributes = []
@@ -261,7 +261,7 @@ class MultiParameterAttributeTest < ActiveRecord::TestCase
         topic = Topic.find(1)
         topic.attributes = attributes
         assert_equal Time.zone.local(2000, 1, 1, 16, 24, 0), topic.bonus_time
-        assert_not topic.bonus_time.utc?
+        assert_not_predicate topic.bonus_time, :utc?
 
         attributes = {
           "written_on(1i)" => "2000", "written_on(2i)" => "", "written_on(3i)" => "",
diff --git a/activerecord/test/cases/nested_attributes_test.rb b/activerecord/test/cases/nested_attributes_test.rb
index a2ccb603a9..1ed3a61bbb 100644
--- a/activerecord/test/cases/nested_attributes_test.rb
+++ b/activerecord/test/cases/nested_attributes_test.rb
@@ -36,7 +36,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     pirate.birds_with_reject_all_blank_attributes = [{ name: "", color: "", _destroy: "0" }]
     pirate.save!
 
-    assert pirate.birds_with_reject_all_blank.empty?
+    assert_empty pirate.birds_with_reject_all_blank
   end
 
   def test_should_not_build_a_new_record_if_reject_all_blank_returns_false
@@ -44,7 +44,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     pirate.birds_with_reject_all_blank_attributes = [{ name: "", color: "" }]
     pirate.save!
 
-    assert pirate.birds_with_reject_all_blank.empty?
+    assert_empty pirate.birds_with_reject_all_blank
   end
 
   def test_should_build_a_new_record_if_reject_all_blank_does_not_return_false
@@ -152,7 +152,7 @@ class TestNestedAttributesInGeneral < ActiveRecord::TestCase
     man = Man.create(name: "Jon")
     interest = man.interests.create(topic: "the ladies")
     man.update(interests_attributes: { _destroy: "1", id: interest.id })
-    assert man.reload.interests.empty?
+    assert_empty man.reload.interests
   end
 
   def test_reject_if_is_not_short_circuited_if_allow_destroy_is_false
@@ -240,7 +240,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
     @ship.destroy
     @pirate.reload.ship_attributes = { name: "Davy Jones Gold Dagger" }
 
-    assert !@pirate.ship.persisted?
+    assert_not_predicate @pirate.ship, :persisted?
     assert_equal "Davy Jones Gold Dagger", @pirate.ship.name
   end
 
@@ -261,7 +261,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_replace_an_existing_record_if_there_is_no_id
     @pirate.reload.ship_attributes = { name: "Davy Jones Gold Dagger" }
 
-    assert !@pirate.ship.persisted?
+    assert_not_predicate @pirate.ship, :persisted?
     assert_equal "Davy Jones Gold Dagger", @pirate.ship.name
     assert_equal "Nights Dirty Lightning", @ship.name
   end
@@ -335,7 +335,7 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_also_work_with_a_HashWithIndifferentAccess
     @pirate.ship_attributes = ActiveSupport::HashWithIndifferentAccess.new(id: @ship.id, name: "Davy Jones Gold Dagger")
 
-    assert @pirate.ship.persisted?
+    assert_predicate @pirate.ship, :persisted?
     assert_equal "Davy Jones Gold Dagger", @pirate.ship.name
   end
 
@@ -350,12 +350,12 @@ class TestNestedAttributesOnAHasOneAssociation < ActiveRecord::TestCase
   def test_should_not_destroy_the_associated_model_until_the_parent_is_saved
     @pirate.attributes = { ship_attributes: { id: @ship.id, _destroy: "1" } }
 
-    assert !@pirate.ship.destroyed?
-    assert @pirate.ship.marked_for_destruction?
+    assert_not_predicate @pirate.ship, :destroyed?
+    assert_predicate @pirate.ship, :marked_for_destruction?
 
     @pirate.save
 
-    assert @pirate.ship.destroyed?
+    assert_predicate @pirate.ship, :destroyed?
     assert_nil @pirate.reload.ship
   end
 
@@ -424,7 +424,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
     @pirate.destroy
     @ship.reload.pirate_attributes = { catchphrase: "Arr" }
 
-    assert !@ship.pirate.persisted?
+    assert_not_predicate @ship.pirate, :persisted?
     assert_equal "Arr", @ship.pirate.catchphrase
   end
 
@@ -445,7 +445,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
   def test_should_replace_an_existing_record_if_there_is_no_id
     @ship.reload.pirate_attributes = { catchphrase: "Arr" }
 
-    assert !@ship.pirate.persisted?
+    assert_not_predicate @ship.pirate, :persisted?
     assert_equal "Arr", @ship.pirate.catchphrase
     assert_equal "Aye", @pirate.catchphrase
   end
@@ -550,7 +550,7 @@ class TestNestedAttributesOnABelongsToAssociation < ActiveRecord::TestCase
     @pirate.delete
     @ship.reload.attributes = { update_only_pirate_attributes: { catchphrase: "Arr" } }
 
-    assert !@ship.update_only_pirate.persisted?
+    assert_not_predicate @ship.update_only_pirate, :persisted?
   end
 
   def test_should_update_existing_when_update_only_is_true_and_no_id_is_given
@@ -632,10 +632,10 @@ module NestedAttributesOnACollectionAssociationTests
   def test_should_not_load_association_when_updating_existing_records
     @pirate.reload
     @pirate.send(association_setter, [{ id: @child_1.id, name: "Grace OMalley" }])
-    assert ! @pirate.send(@association_name).loaded?
+    assert_not_predicate @pirate.send(@association_name), :loaded?
 
     @pirate.save
-    assert ! @pirate.send(@association_name).loaded?
+    assert_not_predicate @pirate.send(@association_name), :loaded?
     assert_equal "Grace OMalley", @child_1.reload.name
   end
 
@@ -663,7 +663,7 @@ module NestedAttributesOnACollectionAssociationTests
   def test_should_not_remove_scheduled_destroys_when_loading_association
     @pirate.reload
     @pirate.send(association_setter, [{ id: @child_1.id, _destroy: "1" }])
-    assert @pirate.send(@association_name).load_target.find { |r| r.id == @child_1.id }.marked_for_destruction?
+    assert_predicate @pirate.send(@association_name).load_target.find { |r| r.id == @child_1.id }, :marked_for_destruction?
   end
 
   def test_should_take_a_hash_with_composite_id_keys_and_assign_the_attributes_to_the_associated_models
@@ -705,10 +705,10 @@ module NestedAttributesOnACollectionAssociationTests
       association_getter => { "foo" => { name: "Grace OMalley" }, "bar" => { name: "Privateers Greed" } }
     }
 
-    assert !@pirate.send(@association_name).first.persisted?
+    assert_not_predicate @pirate.send(@association_name).first, :persisted?
     assert_equal "Grace OMalley", @pirate.send(@association_name).first.name
 
-    assert !@pirate.send(@association_name).last.persisted?
+    assert_not_predicate @pirate.send(@association_name).last, :persisted?
     assert_equal "Privateers Greed", @pirate.send(@association_name).last.name
   end
 
@@ -1091,7 +1091,7 @@ class TestHasManyAutosaveAssociationWhichItselfHasAutosaveAssociations < ActiveR
   test "nested singular associations are validated" do
     part = ShipPart.new(name: "Stern", ship_attributes: { name: nil })
 
-    assert_not part.valid?
+    assert_not_predicate part, :valid?
     assert_equal ["Ship name can't be blank"], part.errors.full_messages
   end
 end
diff --git a/activerecord/test/cases/nested_attributes_with_callbacks_test.rb b/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
index f04c68b08f..1d26057fdc 100644
--- a/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
+++ b/activerecord/test/cases/nested_attributes_with_callbacks_test.rb
@@ -63,7 +63,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
 
   # Characterizing when :before_add callback is called
   test ":before_add called for new bird when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = new_bird_attributes
     assert_new_bird_with_callback_called
   end
@@ -80,7 +80,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
   end
 
   test ":before_add not called for identical assignment when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = existing_birds_attributes
     assert_callbacks_not_called
   end
@@ -92,7 +92,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
   end
 
   test ":before_add not called for destroy assignment when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = destroy_bird_attributes
     assert_callbacks_not_called
   end
@@ -111,7 +111,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
   # Ensuring that the records in the association target are updated,
   # whether the association is loaded before or not
   test "Assignment updates records in target when not loaded" do
-    assert_not @pirate.birds_with_add.loaded?
+    assert_not_predicate @pirate.birds_with_add, :loaded?
     @pirate.birds_with_add_attributes = update_new_and_destroy_bird_attributes
     assert_assignment_affects_records_in_target(:birds_with_add)
   end
@@ -124,7 +124,7 @@ class NestedAttributesWithCallbacksTest < ActiveRecord::TestCase
 
   test("Assignment updates records in target when not loaded" \
        " and callback loads target") do
-    assert_not @pirate.birds_with_add_load.loaded?
+    assert_not_predicate @pirate.birds_with_add_load, :loaded?
     @pirate.birds_with_add_load_attributes = update_new_and_destroy_bird_attributes
     assert_assignment_affects_records_in_target(:birds_with_add_load)
   end
diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 0edca96cf5..e4a65a48ca 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -217,7 +217,7 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_destroy_all
     conditions = "author_name = 'Mary'"
     topics_by_mary = Topic.all.merge!(where: conditions, order: "id").to_a
-    assert ! topics_by_mary.empty?
+    assert_not_empty topics_by_mary
 
     assert_difference("Topic.count", -topics_by_mary.size) do
       destroyed = Topic.where(conditions).destroy_all.sort_by(&:id)
@@ -251,9 +251,16 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_equal "The First Topic", topics(:first).becomes(Reply).title
   end
 
+  def test_becomes_after_reload_schema_from_cache
+    Reply.define_attribute_methods
+    Reply.serialize(:content) # invoke reload_schema_from_cache
+    assert_kind_of Reply, topics(:first).becomes(Reply)
+    assert_equal "The First Topic", topics(:first).becomes(Reply).title
+  end
+
   def test_becomes_includes_errors
     company = Company.new(name: nil)
-    assert !company.valid?
+    assert_not_predicate company, :valid?
     original_errors = company.errors
     client = company.becomes(Client)
     assert_equal original_errors.keys, client.errors.keys
@@ -370,8 +377,8 @@ class PersistenceTest < ActiveRecord::TestCase
     developer.destroy
     new_developer = developer.dup
     new_developer.save
-    assert new_developer.persisted?
-    assert_not new_developer.destroyed?
+    assert_predicate new_developer, :persisted?
+    assert_not_predicate new_developer, :destroyed?
   end
 
   def test_create_many
@@ -387,7 +394,7 @@ class PersistenceTest < ActiveRecord::TestCase
     )
     topic = topic.dup # reset @new_record
     assert_nothing_raised { topic.save }
-    assert topic.persisted?
+    assert_predicate topic, :persisted?
     assert_equal "Another New Topic", topic.reload.title
   end
 
@@ -435,7 +442,7 @@ class PersistenceTest < ActiveRecord::TestCase
     topic_reloaded = Topic.instantiate(topic.attributes.merge("does_not_exist" => "test"))
     topic_reloaded.title = "A New Topic"
     assert_nothing_raised { topic_reloaded.save }
-    assert topic_reloaded.persisted?
+    assert_predicate topic_reloaded, :persisted?
     assert_equal "A New Topic", topic_reloaded.reload.title
   end
 
@@ -473,6 +480,22 @@ class PersistenceTest < ActiveRecord::TestCase
     assert_instance_of Reply, Reply.find(reply.id)
   end
 
+  def test_becomes_default_sti_subclass
+    original_type = Topic.columns_hash["type"].default
+    ActiveRecord::Base.connection.change_column_default :topics, :type, "Reply"
+    Topic.reset_column_information
+
+    reply = topics(:second)
+    assert_instance_of Reply, reply
+
+    topic = reply.becomes(Topic)
+    assert_instance_of Topic, topic
+
+  ensure
+    ActiveRecord::Base.connection.change_column_default :topics, :type, original_type
+    Topic.reset_column_information
+  end
+
   def test_update_after_create
     klass = Class.new(Topic) do
       def self.name; "Topic"; end
@@ -502,7 +525,7 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_update_does_not_run_sql_if_record_has_not_changed
     topic = Topic.create(title: "Another New Topic")
     assert_queries(0) { assert topic.update(title: "Another New Topic") }
-    assert_queries(0) { assert topic.update_attributes(title: "Another New Topic") }
+    assert_queries(0) { assert topic.update(title: "Another New Topic") }
   end
 
   def test_delete
@@ -601,63 +624,63 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_delete_new_record
     client = Client.new(name: "37signals")
     client.delete
-    assert client.frozen?
+    assert_predicate client, :frozen?
 
     assert_not client.save
     assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
 
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_delete_record_with_associations
     client = Client.find(3)
     client.delete
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_kind_of Firm, client.firm
 
     assert_not client.save
     assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
 
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_destroy_new_record
     client = Client.new(name: "37signals")
     client.destroy
-    assert client.frozen?
+    assert_predicate client, :frozen?
 
     assert_not client.save
     assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
 
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_destroy_record_with_associations
     client = Client.find(3)
     client.destroy
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_kind_of Firm, client.firm
 
     assert_not client.save
     assert_raise(ActiveRecord::RecordNotSaved) { client.save! }
 
-    assert client.frozen?
+    assert_predicate client, :frozen?
     assert_raise(RuntimeError) { client.name = "something else" }
   end
 
   def test_update_attribute
-    assert !Topic.find(1).approved?
+    assert_not_predicate Topic.find(1), :approved?
     Topic.find(1).update_attribute("approved", true)
-    assert Topic.find(1).approved?
+    assert_predicate Topic.find(1), :approved?
 
     Topic.find(1).update_attribute(:approved, false)
-    assert !Topic.find(1).approved?
+    assert_not_predicate Topic.find(1), :approved?
 
     Topic.find(1).update_attribute(:change_approved_before_save, true)
-    assert Topic.find(1).approved?
+    assert_predicate Topic.find(1), :approved?
   end
 
   def test_update_attribute_for_readonly_attribute
@@ -694,14 +717,14 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_update_column
     topic = Topic.find(1)
     topic.update_column("approved", true)
-    assert topic.approved?
+    assert_predicate topic, :approved?
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
 
     topic.update_column(:approved, false)
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     topic.reload
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
   end
 
   def test_update_column_should_not_use_setter_method
@@ -788,10 +811,10 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_update_columns
     topic = Topic.find(1)
     topic.update_columns("approved" => true, title: "Sebastian Topic")
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_equal "Sebastian Topic", topic.title
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_equal "Sebastian Topic", topic.title
   end
 
@@ -899,54 +922,45 @@ class PersistenceTest < ActiveRecord::TestCase
 
   def test_update
     topic = Topic.find(1)
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     assert_equal "The First Topic", topic.title
 
     topic.update("approved" => true, "title" => "The First Topic Updated")
     topic.reload
-    assert topic.approved?
+    assert_predicate topic, :approved?
     assert_equal "The First Topic Updated", topic.title
 
     topic.update(approved: false, title: "The First Topic")
     topic.reload
-    assert !topic.approved?
-    assert_equal "The First Topic", topic.title
-  end
-
-  def test_update_attributes
-    topic = Topic.find(1)
-    assert !topic.approved?
-    assert_equal "The First Topic", topic.title
-
-    topic.update_attributes("approved" => true, "title" => "The First Topic Updated")
-    topic.reload
-    assert topic.approved?
-    assert_equal "The First Topic Updated", topic.title
-
-    topic.update_attributes(approved: false, title: "The First Topic")
-    topic.reload
-    assert !topic.approved?
+    assert_not_predicate topic, :approved?
     assert_equal "The First Topic", topic.title
 
     error = assert_raise(ActiveRecord::RecordNotUnique, ActiveRecord::StatementInvalid) do
-      topic.update_attributes(id: 3, title: "Hm is it possible?")
+      topic.update(id: 3, title: "Hm is it possible?")
     end
     assert_not_nil error.cause
     assert_not_equal "Hm is it possible?", Topic.find(3).title
 
-    topic.update_attributes(id: 1234)
+    topic.update(id: 1234)
     assert_nothing_raised { topic.reload }
     assert_equal topic.title, Topic.find(1234).title
   end
 
-  def test_update_attributes_parameters
+  def test_update_attributes
+    topic = Topic.find(1)
+    assert_deprecated do
+      topic.update_attributes("title" => "The First Topic Updated")
+    end
+  end
+
+  def test_update_parameters
     topic = Topic.find(1)
     assert_nothing_raised do
-      topic.update_attributes({})
+      topic.update({})
     end
 
     assert_raises(ArgumentError) do
-      topic.update_attributes(nil)
+      topic.update(nil)
     end
   end
 
@@ -972,24 +986,10 @@ class PersistenceTest < ActiveRecord::TestCase
   end
 
   def test_update_attributes!
-    Reply.validates_presence_of(:title)
     reply = Reply.find(2)
-    assert_equal "The Second Topic of the day", reply.title
-    assert_equal "Have a nice day", reply.content
-
-    reply.update_attributes!("title" => "The Second Topic of the day updated", "content" => "Have a nice evening")
-    reply.reload
-    assert_equal "The Second Topic of the day updated", reply.title
-    assert_equal "Have a nice evening", reply.content
-
-    reply.update_attributes!(title: "The Second Topic of the day", content: "Have a nice day")
-    reply.reload
-    assert_equal "The Second Topic of the day", reply.title
-    assert_equal "Have a nice day", reply.content
-
-    assert_raise(ActiveRecord::RecordInvalid) { reply.update_attributes!(title: nil, content: "Have a nice evening") }
-  ensure
-    Reply.clear_validators!
+    assert_deprecated do
+      reply.update_attributes!("title" => "The Second Topic of the day updated")
+    end
   end
 
   def test_destroyed_returns_boolean
@@ -1026,7 +1026,7 @@ class PersistenceTest < ActiveRecord::TestCase
     Topic.find(1).replies << should_be_destroyed_reply
 
     topic = Topic.destroy(1)
-    assert topic.destroyed?
+    assert_predicate topic, :destroyed?
 
     assert_raise(ActiveRecord::RecordNotFound) { Topic.find(1) }
     assert_raise(ActiveRecord::RecordNotFound) { Reply.find(should_be_destroyed_reply.id) }
@@ -1106,13 +1106,13 @@ class PersistenceTest < ActiveRecord::TestCase
   def test_find_via_reload
     post = Post.new
 
-    assert post.new_record?
+    assert_predicate post, :new_record?
 
     post.id = 1
     post.reload
 
     assert_equal "Welcome to the weblog", post.title
-    assert_not post.new_record?
+    assert_not_predicate post, :new_record?
   end
 
   def test_reload_via_querycache
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index 80016fc19d..60dac91ec9 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -207,13 +207,13 @@ class PrimaryKeysTest < ActiveRecord::TestCase
     def test_serial_with_quoted_sequence_name
       column = MixedCaseMonkey.columns_hash[MixedCaseMonkey.primary_key]
       assert_equal "nextval('\"mixed_case_monkeys_monkeyID_seq\"'::regclass)", column.default_function
-      assert column.serial?
+      assert_predicate column, :serial?
     end
 
     def test_serial_with_unquoted_sequence_name
       column = Topic.columns_hash[Topic.primary_key]
       assert_equal "nextval('topics_id_seq'::regclass)", column.default_function
-      assert column.serial?
+      assert_predicate column, :serial?
     end
   end
 end
@@ -430,7 +430,7 @@ if current_adapter?(:PostgreSQLAdapter, :Mysql2Adapter)
       @connection.create_table(:widgets, id: @pk_type, force: true)
       column = @connection.columns(:widgets).find { |c| c.name == "id" }
       assert_equal :integer, column.type
-      assert_not column.bigint?
+      assert_not_predicate column, :bigint?
     end
 
     test "primary key with serial/integer are automatically numbered" do
@@ -449,10 +449,10 @@ if current_adapter?(:PostgreSQLAdapter, :Mysql2Adapter)
       test "primary key column type with options" do
         @connection.create_table(:widgets, id: :primary_key, limit: 4, unsigned: true, force: true)
         column = @connection.columns(:widgets).find { |c| c.name == "id" }
-        assert column.auto_increment?
+        assert_predicate column, :auto_increment?
         assert_equal :integer, column.type
-        assert_not column.bigint?
-        assert column.unsigned?
+        assert_not_predicate column, :bigint?
+        assert_predicate column, :unsigned?
 
         schema = dump_table_schema "widgets"
         assert_match %r{create_table "widgets", id: :integer, unsigned: true, }, schema
@@ -461,10 +461,10 @@ if current_adapter?(:PostgreSQLAdapter, :Mysql2Adapter)
       test "bigint primary key with unsigned" do
         @connection.create_table(:widgets, id: :bigint, unsigned: true, force: true)
         column = @connection.columns(:widgets).find { |c| c.name == "id" }
-        assert column.auto_increment?
+        assert_predicate column, :auto_increment?
         assert_equal :integer, column.type
-        assert column.bigint?
-        assert column.unsigned?
+        assert_predicate column, :bigint?
+        assert_predicate column, :unsigned?
 
         schema = dump_table_schema "widgets"
         assert_match %r{create_table "widgets", id: :bigint, unsigned: true, }, schema
diff --git a/activerecord/test/cases/query_cache_test.rb b/activerecord/test/cases/query_cache_test.rb
index ad05f70933..d635a47c0e 100644
--- a/activerecord/test/cases/query_cache_test.rb
+++ b/activerecord/test/cases/query_cache_test.rb
@@ -82,7 +82,7 @@ class QueryCacheTest < ActiveRecord::TestCase
           assert_cache :off, conn
         end
 
-        assert !ActiveRecord::Base.connection.nil?
+        assert_not_predicate ActiveRecord::Base.connection, :nil?
         assert_cache :off
 
         middleware {
@@ -320,6 +320,17 @@ class QueryCacheTest < ActiveRecord::TestCase
     end
   end
 
+  def test_cache_is_available_when_connection_is_connected
+    conf = ActiveRecord::Base.configurations
+
+    ActiveRecord::Base.configurations = {}
+    Task.cache do
+      assert_queries(1) { Task.find(1); Task.find(1) }
+    end
+  ensure
+    ActiveRecord::Base.configurations = conf
+  end
+
   def test_cache_is_available_when_using_a_not_connected_connection
     skip "In-Memory DB can't test for using a not connected connection" if in_memory_db?
     with_temporary_connection_pool do
@@ -327,7 +338,7 @@ class QueryCacheTest < ActiveRecord::TestCase
       conf = ActiveRecord::Base.configurations["arunit"].merge("name" => "test2")
       ActiveRecord::Base.connection_handler.establish_connection(conf)
       Task.connection_specification_name = "test2"
-      refute Task.connected?
+      assert_not_predicate Task, :connected?
 
       Task.cache do
         begin
@@ -366,7 +377,7 @@ class QueryCacheTest < ActiveRecord::TestCase
     post = Post.first
 
     Post.transaction do
-      post.update_attributes(title: "rollback")
+      post.update(title: "rollback")
       assert_equal 1, Post.where(title: "rollback").to_a.count
       raise ActiveRecord::Rollback
     end
@@ -379,7 +390,7 @@ class QueryCacheTest < ActiveRecord::TestCase
 
     begin
       Post.transaction do
-        post.update_attributes(title: "rollback")
+        post.update(title: "rollback")
         assert_equal 1, Post.where(title: "rollback").to_a.count
         raise "broken"
       end
@@ -414,20 +425,20 @@ class QueryCacheTest < ActiveRecord::TestCase
   def test_query_cache_does_not_establish_connection_if_unconnected
     with_temporary_connection_pool do
       ActiveRecord::Base.clear_active_connections!
-      refute ActiveRecord::Base.connection_handler.active_connections? # sanity check
+      assert_not ActiveRecord::Base.connection_handler.active_connections? # sanity check
 
       middleware {
-        refute ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in setup"
+        assert_not ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in setup"
       }.call({})
 
-      refute ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in cleanup"
+      assert_not ActiveRecord::Base.connection_handler.active_connections?, "QueryCache forced ActiveRecord::Base to establish a connection in cleanup"
     end
   end
 
   def test_query_cache_is_enabled_on_connections_established_after_middleware_runs
     with_temporary_connection_pool do
       ActiveRecord::Base.clear_active_connections!
-      refute ActiveRecord::Base.connection_handler.active_connections? # sanity check
+      assert_not ActiveRecord::Base.connection_handler.active_connections? # sanity check
 
       middleware {
         assert ActiveRecord::Base.connection.query_cache_enabled, "QueryCache did not get lazily enabled"
@@ -444,8 +455,8 @@ class QueryCacheTest < ActiveRecord::TestCase
         assert ActiveRecord::Base.connection.query_cache_enabled
 
         Thread.new {
-          refute ActiveRecord::Base.connection_pool.query_cache_enabled
-          refute ActiveRecord::Base.connection.query_cache_enabled
+          assert_not ActiveRecord::Base.connection_pool.query_cache_enabled
+          assert_not ActiveRecord::Base.connection.query_cache_enabled
         }.join
       }.call({})
 
@@ -562,7 +573,7 @@ class QueryCacheExpiryTest < ActiveRecord::TestCase
     assert_called(ActiveRecord::Base.connection, :clear_query_cache, times: 2) do
       ActiveRecord::Base.cache do
         p = Post.find(1)
-        assert p.categories.any?
+        assert_predicate p.categories, :any?
         p.categories.delete_all
       end
     end
diff --git a/activerecord/test/cases/readonly_test.rb b/activerecord/test/cases/readonly_test.rb
index d1b85cb4ef..383e43ed55 100644
--- a/activerecord/test/cases/readonly_test.rb
+++ b/activerecord/test/cases/readonly_test.rb
@@ -16,10 +16,10 @@ class ReadOnlyTest < ActiveRecord::TestCase
 
   def test_cant_save_readonly_record
     dev = Developer.find(1)
-    assert !dev.readonly?
+    assert_not_predicate dev, :readonly?
 
     dev.readonly!
-    assert dev.readonly?
+    assert_predicate dev, :readonly?
 
     assert_nothing_raised do
       dev.name = "Luscious forbidden fruit."
@@ -54,7 +54,7 @@ class ReadOnlyTest < ActiveRecord::TestCase
 
   def test_has_many_find_readonly
     post = Post.find(1)
-    assert !post.comments.empty?
+    assert_not_empty post.comments
     assert !post.comments.any?(&:readonly?)
     assert !post.comments.to_a.any?(&:readonly?)
     assert post.comments.readonly(true).all?(&:readonly?)
@@ -66,44 +66,44 @@ class ReadOnlyTest < ActiveRecord::TestCase
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly_while_finding_by_id
-    assert !posts(:welcome).people.find(1).readonly?
+    assert_not_predicate posts(:welcome).people.find(1), :readonly?
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly_while_finding_first
-    assert !posts(:welcome).people.first.readonly?
+    assert_not_predicate posts(:welcome).people.first, :readonly?
   end
 
   def test_has_many_with_through_is_not_implicitly_marked_readonly_while_finding_last
-    assert !posts(:welcome).people.last.readonly?
+    assert_not_predicate posts(:welcome).people.last, :readonly?
   end
 
   def test_readonly_scoping
     Post.where("1=1").scoping do
-      assert !Post.find(1).readonly?
-      assert Post.readonly(true).find(1).readonly?
-      assert !Post.readonly(false).find(1).readonly?
+      assert_not_predicate Post.find(1), :readonly?
+      assert_predicate Post.readonly(true).find(1), :readonly?
+      assert_not_predicate Post.readonly(false).find(1), :readonly?
     end
 
     Post.joins("   ").scoping do
-      assert !Post.find(1).readonly?
-      assert Post.readonly.find(1).readonly?
-      assert !Post.readonly(false).find(1).readonly?
+      assert_not_predicate Post.find(1), :readonly?
+      assert_predicate Post.readonly.find(1), :readonly?
+      assert_not_predicate Post.readonly(false).find(1), :readonly?
     end
 
     # Oracle barfs on this because the join includes unqualified and
     # conflicting column names
     unless current_adapter?(:OracleAdapter)
       Post.joins(", developers").scoping do
-        assert_not Post.find(1).readonly?
-        assert Post.readonly.find(1).readonly?
-        assert !Post.readonly(false).find(1).readonly?
+        assert_not_predicate Post.find(1), :readonly?
+        assert_predicate Post.readonly.find(1), :readonly?
+        assert_not_predicate Post.readonly(false).find(1), :readonly?
       end
     end
 
     Post.readonly(true).scoping do
-      assert Post.find(1).readonly?
-      assert Post.readonly.find(1).readonly?
-      assert !Post.readonly(false).find(1).readonly?
+      assert_predicate Post.find(1), :readonly?
+      assert_predicate Post.readonly.find(1), :readonly?
+      assert_not_predicate Post.readonly(false).find(1), :readonly?
     end
   end
 
@@ -111,10 +111,10 @@ class ReadOnlyTest < ActiveRecord::TestCase
     developer = Developer.find(1)
     project   = Post.find(1)
 
-    assert !developer.projects.all_as_method.first.readonly?
-    assert !developer.projects.all_as_scope.first.readonly?
+    assert_not_predicate developer.projects.all_as_method.first, :readonly?
+    assert_not_predicate developer.projects.all_as_scope.first, :readonly?
 
-    assert !project.comments.all_as_method.first.readonly?
-    assert !project.comments.all_as_scope.first.readonly?
+    assert_not_predicate project.comments.all_as_method.first, :readonly?
+    assert_not_predicate project.comments.all_as_scope.first, :readonly?
   end
 end
diff --git a/activerecord/test/cases/reaper_test.rb b/activerecord/test/cases/reaper_test.rb
index 6c7727ab1b..61cb0f130d 100644
--- a/activerecord/test/cases/reaper_test.rb
+++ b/activerecord/test/cases/reaper_test.rb
@@ -79,14 +79,14 @@ module ActiveRecord
         end
         Thread.pass while conn.nil?
 
-        assert conn.in_use?
+        assert_predicate conn, :in_use?
 
         child.terminate
 
         while conn.in_use?
           Thread.pass
         end
-        assert !conn.in_use?
+        assert_not_predicate conn, :in_use?
       end
     end
   end
diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index e78c3cee8a..ed19192ad9 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -66,6 +66,9 @@ class ReflectionTest < ActiveRecord::TestCase
 
   def test_column_string_type_and_limit
     assert_equal :string, @first.column_for_attribute("title").type
+    assert_equal :string, @first.column_for_attribute(:title).type
+    assert_equal :string, @first.type_for_attribute("title").type
+    assert_equal :string, @first.type_for_attribute(:title).type
     assert_equal 250, @first.column_for_attribute("title").limit
   end
 
@@ -81,6 +84,9 @@ class ReflectionTest < ActiveRecord::TestCase
 
   def test_integer_columns
     assert_equal :integer, @first.column_for_attribute("id").type
+    assert_equal :integer, @first.column_for_attribute(:id).type
+    assert_equal :integer, @first.type_for_attribute("id").type
+    assert_equal :integer, @first.type_for_attribute(:id).type
   end
 
   def test_non_existent_columns_return_null_object
@@ -89,6 +95,9 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal "attribute_that_doesnt_exist", column.name
     assert_nil column.sql_type
     assert_nil column.type
+
+    column = @first.column_for_attribute(:attribute_that_doesnt_exist)
+    assert_instance_of ActiveRecord::ConnectionAdapters::NullColumn, column
   end
 
   def test_non_existent_types_are_identity_types
@@ -98,6 +107,11 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal object, type.deserialize(object)
     assert_equal object, type.cast(object)
     assert_equal object, type.serialize(object)
+
+    type = @first.type_for_attribute(:attribute_that_doesnt_exist)
+    assert_equal object, type.deserialize(object)
+    assert_equal object, type.cast(object)
+    assert_equal object, type.serialize(object)
   end
 
   def test_reflection_klass_for_nested_class_name
@@ -149,7 +163,7 @@ class ReflectionTest < ActiveRecord::TestCase
     expected = Pirate.reflect_on_all_associations.select { |r| r.options[:autosave] }
     received = Pirate.reflect_on_all_autosave_associations
 
-    assert !received.empty?
+    assert_not_empty received
     assert_not_equal Pirate.reflect_on_all_associations.length, received.length
     assert_equal expected, received
   end
@@ -301,12 +315,12 @@ class ReflectionTest < ActiveRecord::TestCase
   end
 
   def test_nested?
-    assert !Author.reflect_on_association(:comments).nested?
-    assert Author.reflect_on_association(:tags).nested?
+    assert_not_predicate Author.reflect_on_association(:comments), :nested?
+    assert_predicate Author.reflect_on_association(:tags), :nested?
 
     # Only goes :through once, but the through_reflection is a has_and_belongs_to_many, so this is
     # a nested through association
-    assert Category.reflect_on_association(:post_comments).nested?
+    assert_predicate Category.reflect_on_association(:post_comments), :nested?
   end
 
   def test_association_primary_key
@@ -354,36 +368,36 @@ class ReflectionTest < ActiveRecord::TestCase
   end
 
   def test_collection_association
-    assert Pirate.reflect_on_association(:birds).collection?
-    assert Pirate.reflect_on_association(:parrots).collection?
+    assert_predicate Pirate.reflect_on_association(:birds), :collection?
+    assert_predicate Pirate.reflect_on_association(:parrots), :collection?
 
-    assert !Pirate.reflect_on_association(:ship).collection?
-    assert !Ship.reflect_on_association(:pirate).collection?
+    assert_not_predicate Pirate.reflect_on_association(:ship), :collection?
+    assert_not_predicate Ship.reflect_on_association(:pirate), :collection?
   end
 
   def test_default_association_validation
-    assert ActiveRecord::Reflection.create(:has_many, :clients, nil, {}, Firm).validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, {}, Firm), :validate?
 
-    assert !ActiveRecord::Reflection.create(:has_one, :client, nil, {}, Firm).validate?
-    assert !ActiveRecord::Reflection.create(:belongs_to, :client, nil, {}, Firm).validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, {}, Firm), :validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, {}, Firm), :validate?
   end
 
   def test_always_validate_association_if_explicit
-    assert ActiveRecord::Reflection.create(:has_one, :client, nil, { validate: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:belongs_to, :client, nil, { validate: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:has_many, :clients, nil, { validate: true }, Firm).validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, { validate: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, { validate: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { validate: true }, Firm), :validate?
   end
 
   def test_validate_association_if_autosave
-    assert ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true }, Firm).validate?
-    assert ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true }, Firm).validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true }, Firm), :validate?
+    assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true }, Firm), :validate?
   end
 
   def test_never_validate_association_if_explicit
-    assert !ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true, validate: false }, Firm).validate?
-    assert !ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true, validate: false }, Firm).validate?
-    assert !ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true, validate: false }, Firm).validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:has_one, :client, nil, { autosave: true, validate: false }, Firm), :validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:belongs_to, :client, nil, { autosave: true, validate: false }, Firm), :validate?
+    assert_not_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { autosave: true, validate: false }, Firm), :validate?
   end
 
   def test_foreign_key
diff --git a/activerecord/test/cases/relation/merging_test.rb b/activerecord/test/cases/relation/merging_test.rb
index f31df40c91..074ce9454f 100644
--- a/activerecord/test/cases/relation/merging_test.rb
+++ b/activerecord/test/cases/relation/merging_test.rb
@@ -58,7 +58,7 @@ class RelationMergingTest < ActiveRecord::TestCase
 
   def test_relation_merging_with_locks
     devs = Developer.lock.where("salary >= 80000").order("id DESC").merge(Developer.limit(2))
-    assert devs.locked?
+    assert_predicate devs, :locked?
   end
 
   def test_relation_merging_with_preload
@@ -113,9 +113,9 @@ class RelationMergingTest < ActiveRecord::TestCase
 
   def test_merging_with_from_clause
     relation = Post.all
-    assert relation.from_clause.empty?
+    assert_empty relation.from_clause
     relation = relation.merge(Post.from("posts"))
-    refute relation.from_clause.empty?
+    assert_not_empty relation.from_clause
   end
 end
 
diff --git a/activerecord/test/cases/relation/mutation_test.rb b/activerecord/test/cases/relation/mutation_test.rb
index ad3700b73a..1428b3e132 100644
--- a/activerecord/test/cases/relation/mutation_test.rb
+++ b/activerecord/test/cases/relation/mutation_test.rb
@@ -25,7 +25,7 @@ module ActiveRecord
     test "#order! with symbol prepends the table name" do
       assert relation.order!(:name).equal?(relation)
       node = relation.order_values.first
-      assert node.ascending?
+      assert_predicate node, :ascending?
       assert_equal :name, node.expr.name
       assert_equal "posts", node.expr.relation.name
     end
@@ -88,7 +88,7 @@ module ActiveRecord
       assert relation.reorder!(:name).equal?(relation)
       node = relation.order_values.first
 
-      assert node.ascending?
+      assert_predicate node, :ascending?
       assert_equal :name, node.expr.name
       assert_equal "posts", node.expr.relation.name
     end
@@ -139,7 +139,7 @@ module ActiveRecord
 
     private
       def relation
-        @relation ||= Relation.new(FakeKlass, Post.arel_table, Post.predicate_builder)
+        @relation ||= Relation.new(FakeKlass)
       end
   end
 end
diff --git a/activerecord/test/cases/relation/select_test.rb b/activerecord/test/cases/relation/select_test.rb
new file mode 100644
index 0000000000..0577e6bfdb
--- /dev/null
+++ b/activerecord/test/cases/relation/select_test.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/post"
+
+module ActiveRecord
+  class SelectTest < ActiveRecord::TestCase
+    fixtures :posts
+
+    def test_select_with_nil_agrument
+      expected = Post.select(:title).to_sql
+      assert_equal expected, Post.select(nil).select(:title).to_sql
+    end
+  end
+end
diff --git a/activerecord/test/cases/relation/where_clause_test.rb b/activerecord/test/cases/relation/where_clause_test.rb
index e5eb159d36..8703d238a0 100644
--- a/activerecord/test/cases/relation/where_clause_test.rb
+++ b/activerecord/test/cases/relation/where_clause_test.rb
@@ -75,8 +75,8 @@ class ActiveRecord::Relation
     end
 
     test "a clause knows if it is empty" do
-      assert WhereClause.empty.empty?
-      assert_not WhereClause.new(["anything"]).empty?
+      assert_empty WhereClause.empty
+      assert_not_empty WhereClause.new(["anything"])
     end
 
     test "invert cannot handle nil" do
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index dbf3389774..4e75371147 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -11,19 +11,19 @@ module ActiveRecord
     fixtures :posts, :comments, :authors, :author_addresses, :ratings
 
     def test_construction
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass, table: :b)
       assert_equal FakeKlass, relation.klass
       assert_equal :b, relation.table
       assert !relation.loaded, "relation is not loaded"
     end
 
     def test_responds_to_model_and_returns_klass
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal FakeKlass, relation.model
     end
 
     def test_initialize_single_values
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       (Relation::SINGLE_VALUE_METHODS - [:create_with]).each do |method|
         assert_nil relation.send("#{method}_value"), method.to_s
       end
@@ -33,7 +33,7 @@ module ActiveRecord
     end
 
     def test_multi_value_initialize
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       Relation::MULTI_VALUE_METHODS.each do |method|
         values = relation.send("#{method}_values")
         assert_equal [], values, method.to_s
@@ -42,29 +42,29 @@ module ActiveRecord
     end
 
     def test_extensions
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal [], relation.extensions
     end
 
     def test_empty_where_values_hash
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal({}, relation.where_values_hash)
     end
 
     def test_has_values
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation.where!(id: 10)
       assert_equal({ "id" => 10 }, relation.where_values_hash)
     end
 
     def test_values_wrong_table
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation.where! Comment.arel_table[:id].eq(10)
       assert_equal({}, relation.where_values_hash)
     end
 
     def test_tree_is_not_traversed
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       left     = relation.table[:id].eq(10)
       right    = relation.table[:id].eq(10)
       combine  = left.or(right)
@@ -73,18 +73,18 @@ module ActiveRecord
     end
 
     def test_scope_for_create
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal({}, relation.scope_for_create)
     end
 
     def test_create_with_value
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation.create_with_value = { hello: "world" }
       assert_equal({ "hello" => "world" }, relation.scope_for_create)
     end
 
     def test_create_with_value_with_wheres
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       assert_equal({}, relation.scope_for_create)
 
       relation.where!(id: 10)
@@ -95,11 +95,11 @@ module ActiveRecord
     end
 
     def test_empty_scope
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
-      assert relation.empty_scope?
+      relation = Relation.new(Post)
+      assert_predicate relation, :empty_scope?
 
       relation.merge!(relation)
-      assert relation.empty_scope?
+      assert_predicate relation, :empty_scope?
     end
 
     def test_bad_constants_raise_errors
@@ -109,31 +109,31 @@ module ActiveRecord
     end
 
     def test_empty_eager_loading?
-      relation = Relation.new(FakeKlass, :b, nil)
-      assert !relation.eager_loading?
+      relation = Relation.new(FakeKlass)
+      assert_not_predicate relation, :eager_loading?
     end
 
     def test_eager_load_values
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       relation.eager_load! :b
-      assert relation.eager_loading?
+      assert_predicate relation, :eager_loading?
     end
 
     def test_references_values
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       assert_equal [], relation.references_values
       relation = relation.references(:foo).references(:omg, :lol)
       assert_equal ["foo", "omg", "lol"], relation.references_values
     end
 
     def test_references_values_dont_duplicate
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       relation = relation.references(:foo).references(:foo)
       assert_equal ["foo"], relation.references_values
     end
 
     test "merging a hash into a relation" do
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder)
+      relation = Relation.new(Post)
       relation = relation.merge where: { name: :lol }, readonly: true
 
       assert_equal({ "name" => :lol }, relation.where_clause.to_h)
@@ -141,7 +141,7 @@ module ActiveRecord
     end
 
     test "merging an empty hash into a relation" do
-      assert_equal Relation::WhereClause.empty, Relation.new(FakeKlass, :b, nil).merge({}).where_clause
+      assert_equal Relation::WhereClause.empty, Relation.new(FakeKlass).merge({}).where_clause
     end
 
     test "merging a hash with unknown keys raises" do
@@ -149,7 +149,7 @@ module ActiveRecord
     end
 
     test "merging nil or false raises" do
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
 
       e = assert_raises(ArgumentError) do
         relation = relation.merge nil
@@ -165,7 +165,7 @@ module ActiveRecord
     end
 
     test "#values returns a dup of the values" do
-      relation = Relation.new(Post, Post.arel_table, Post.predicate_builder).where!(name: :foo)
+      relation = Relation.new(Post).where!(name: :foo)
       values   = relation.values
 
       values[:where] = nil
@@ -173,7 +173,7 @@ module ActiveRecord
     end
 
     test "relations can be created with a values hash" do
-      relation = Relation.new(FakeKlass, :b, nil, select: [:foo])
+      relation = Relation.new(FakeKlass, values: { select: [:foo] })
       assert_equal [:foo], relation.select_values
     end
 
@@ -185,13 +185,13 @@ module ActiveRecord
         end
       end
 
-      relation = Relation.new(klass, :b, nil)
+      relation = Relation.new(klass)
       relation.merge!(where: ["foo = ?", "bar"])
       assert_equal Relation::WhereClause.new(["foo = bar"]), relation.where_clause
     end
 
     def test_merging_readonly_false
-      relation = Relation.new(FakeKlass, :b, nil)
+      relation = Relation.new(FakeKlass)
       readonly_false_relation = relation.readonly(false)
       # test merging in both directions
       assert_equal false, relation.merge(readonly_false_relation).readonly_value
@@ -235,17 +235,17 @@ module ActiveRecord
 
     def test_merge_raises_with_invalid_argument
       assert_raises ArgumentError do
-        relation = Relation.new(FakeKlass, :b, nil)
+        relation = Relation.new(FakeKlass)
         relation.merge(true)
       end
     end
 
     def test_respond_to_for_non_selected_element
       post = Post.select(:title).first
-      assert_equal false, post.respond_to?(:body), "post should not respond_to?(:body) since invoking it raises exception"
+      assert_not_respond_to post, :body, "post should not respond_to?(:body) since invoking it raises exception"
 
       silence_warnings { post = Post.select("'title' as post_title").first }
-      assert_equal false, post.respond_to?(:title), "post should not respond_to?(:body) since invoking it raises exception"
+      assert_not_respond_to post, :title, "post should not respond_to?(:body) since invoking it raises exception"
     end
 
     def test_select_quotes_when_using_from_clause
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 7785f8c99b..18e0bed5b6 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -22,6 +22,7 @@ require "models/reader"
 require "models/category"
 require "models/categorization"
 require "models/edge"
+require "models/subscriber"
 
 class RelationTest < ActiveRecord::TestCase
   fixtures :authors, :author_addresses, :topics, :entrants, :developers, :companies, :developers_projects, :accounts, :categories, :categorizations, :categories_posts, :posts, :comments, :tags, :taggings, :cars, :minivans
@@ -56,7 +57,7 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_dynamic_finder
     x = Post.where("author_id = ?", 1)
-    assert x.klass.respond_to?(:find_by_id), "@klass should handle dynamic finders"
+    assert_respond_to x.klass, :find_by_id
   end
 
   def test_multivalue_where
@@ -98,7 +99,7 @@ class RelationTest < ActiveRecord::TestCase
       2.times { assert_equal 5, topics.to_a.size }
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_scoped_first
@@ -108,7 +109,7 @@ class RelationTest < ActiveRecord::TestCase
       2.times { assert_equal "The First Topic", topics.first.title }
     end
 
-    assert ! topics.loaded?
+    assert_not_predicate topics, :loaded?
   end
 
   def test_loaded_first
@@ -119,7 +120,7 @@ class RelationTest < ActiveRecord::TestCase
       assert_equal "The First Topic", topics.first.title
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_loaded_first_with_limit
@@ -131,7 +132,7 @@ class RelationTest < ActiveRecord::TestCase
                     "The Second Topic of the day"], topics.first(2).map(&:title)
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_first_get_more_than_available
@@ -152,14 +153,14 @@ class RelationTest < ActiveRecord::TestCase
       2.times { topics.to_a }
     end
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
 
     original_size = topics.to_a.size
     Topic.create! title: "fake"
 
     assert_queries(1) { topics.reload }
     assert_equal original_size + 1, topics.size
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   def test_finding_with_subquery
@@ -501,12 +502,12 @@ class RelationTest < ActiveRecord::TestCase
     relation = Topic.all
 
     ["find_by_title", "find_by_title_and_author_name"].each do |method|
-      assert_respond_to relation, method, "Topic.all should respond to #{method.inspect}"
+      assert_respond_to relation, method
     end
   end
 
   def test_respond_to_class_methods_and_scopes
-    assert Topic.all.respond_to?(:by_lifo)
+    assert_respond_to Topic.all, :by_lifo
   end
 
   def test_find_with_readonly_option
@@ -601,7 +602,7 @@ class RelationTest < ActiveRecord::TestCase
     reader = Reader.create! post_id: post.id, person_id: 1
     comment = Comment.create! post_id: post.id, body: "body"
 
-    assert !comment.respond_to?(:readers)
+    assert_not_respond_to comment, :readers
 
     post_rel = Post.preload(:readers).joins(:readers).where(title: "Uhuu")
     result_comment = Comment.joins(:post).merge(post_rel).to_a.first
@@ -722,7 +723,7 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_find_in_empty_array
     authors = Author.all.where(id: [])
-    assert authors.to_a.blank?
+    assert_predicate authors.to_a, :blank?
   end
 
   def test_where_with_ar_object
@@ -863,19 +864,19 @@ class RelationTest < ActiveRecord::TestCase
 
     # Force load
     assert_equal [authors(:david)], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
 
     assert_difference("Author.count", -1) { davids.destroy_all }
 
     assert_equal [], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
   end
 
   def test_delete_all
     davids = Author.where(name: "David")
 
     assert_difference("Author.count", -1) { davids.delete_all }
-    assert ! davids.loaded?
+    assert_not_predicate davids, :loaded?
   end
 
   def test_delete_all_loaded
@@ -883,12 +884,12 @@ class RelationTest < ActiveRecord::TestCase
 
     # Force load
     assert_equal [authors(:david)], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
 
     assert_difference("Author.count", -1) { davids.delete_all }
 
     assert_equal [], davids.to_a
-    assert davids.loaded?
+    assert_predicate davids, :loaded?
   end
 
   def test_delete_all_with_unpermitted_relation_raises_error
@@ -902,9 +903,9 @@ class RelationTest < ActiveRecord::TestCase
 
     assert_equal 11, posts.count(:all)
     assert_equal 11, posts.size
-    assert posts.any?
-    assert posts.many?
-    assert_not posts.empty?
+    assert_predicate posts, :any?
+    assert_predicate posts, :many?
+    assert_not_empty posts
   end
 
   def test_select_takes_a_variable_list_of_args
@@ -950,7 +951,7 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal author.posts.where(author_id: author.id).size, posts.count
 
     assert_equal 0, author.posts.where(author_id: another_author.id).size
-    assert author.posts.where(author_id: another_author.id).empty?
+    assert_empty author.posts.where(author_id: another_author.id)
   end
 
   def test_count_with_distinct
@@ -969,6 +970,12 @@ class RelationTest < ActiveRecord::TestCase
     assert_queries(1) { assert_equal 8, posts.load.size }
   end
 
+  def test_size_with_eager_loading_and_custom_order
+    posts = Post.includes(:comments).order("comments.id")
+    assert_queries(1) { assert_equal 11, posts.size }
+    assert_queries(1) { assert_equal 11, posts.load.size }
+  end
+
   def test_update_all_with_scope
     tag = Tag.first
     Post.tagged_with(tag.id).update_all title: "rofl"
@@ -1000,7 +1007,7 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.all
 
     assert_queries(1) { assert_equal 11, posts.size }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
@@ -1011,7 +1018,7 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.limit(10)
 
     assert_queries(1) { assert_equal 10, posts.size }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
@@ -1022,7 +1029,7 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.limit(0)
 
     assert_no_queries { assert_equal 0, posts.size }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     posts.load # force load
     assert_no_queries { assert_equal 0, posts.size }
@@ -1032,7 +1039,7 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.limit(0)
 
     assert_no_queries { assert_equal true, posts.empty? }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
   end
 
   def test_count_complex_chained_relations
@@ -1046,11 +1053,11 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.all
 
     assert_queries(1) { assert_equal false, posts.empty? }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     no_posts = posts.where(title: "")
     assert_queries(1) { assert_equal true, no_posts.empty? }
-    assert ! no_posts.loaded?
+    assert_not_predicate no_posts, :loaded?
 
     best_posts = posts.where(comments_count: 0)
     best_posts.load # force load
@@ -1061,11 +1068,11 @@ class RelationTest < ActiveRecord::TestCase
     posts = Post.select("comments_count").where("id is not null").group("author_id").where("comments_count > 0")
 
     assert_queries(1) { assert_equal false, posts.empty? }
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     no_posts = posts.where(title: "")
     assert_queries(1) { assert_equal true, no_posts.empty? }
-    assert ! no_posts.loaded?
+    assert_not_predicate no_posts, :loaded?
   end
 
   def test_any
@@ -1081,13 +1088,13 @@ class RelationTest < ActiveRecord::TestCase
 
     assert_queries(3) do
       assert posts.any? # Uses COUNT()
-      assert ! posts.where(id: nil).any?
+      assert_not_predicate posts.where(id: nil), :any?
 
       assert posts.any? { |p| p.id > 0 }
       assert ! posts.any? { |p| p.id <= 0 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_many
@@ -1099,14 +1106,14 @@ class RelationTest < ActiveRecord::TestCase
       assert ! posts.many? { |p| p.id < 2 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_many_with_limits
     posts = Post.all
 
-    assert posts.many?
-    assert ! posts.limit(1).many?
+    assert_predicate posts, :many?
+    assert_not_predicate posts.limit(1), :many?
   end
 
   def test_none?
@@ -1115,14 +1122,14 @@ class RelationTest < ActiveRecord::TestCase
       assert ! posts.none? # Uses COUNT()
     end
 
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     assert_queries(1) do
       assert posts.none? { |p| p.id < 0 }
       assert ! posts.none? { |p| p.id == 1 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_one
@@ -1131,14 +1138,14 @@ class RelationTest < ActiveRecord::TestCase
       assert ! posts.one? # Uses COUNT()
     end
 
-    assert ! posts.loaded?
+    assert_not_predicate posts, :loaded?
 
     assert_queries(1) do
       assert ! posts.one? { |p| p.id < 3 }
       assert posts.one? { |p| p.id == 1 }
     end
 
-    assert posts.loaded?
+    assert_predicate posts, :loaded?
   end
 
   def test_to_a_should_dup_target
@@ -1171,10 +1178,10 @@ class RelationTest < ActiveRecord::TestCase
 
     sparrow = birds.create
     assert_kind_of Bird, sparrow
-    assert !sparrow.persisted?
+    assert_not_predicate sparrow, :persisted?
 
     hen = birds.where(name: "hen").create
-    assert hen.persisted?
+    assert_predicate hen, :persisted?
     assert_equal "hen", hen.name
   end
 
@@ -1185,7 +1192,7 @@ class RelationTest < ActiveRecord::TestCase
 
     hen = birds.where(name: "hen").create!
     assert_kind_of Bird, hen
-    assert hen.persisted?
+    assert_predicate hen, :persisted?
     assert_equal "hen", hen.name
   end
 
@@ -1201,27 +1208,27 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_create
     parrot = Bird.where(color: "green").first_or_create(name: "parrot")
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "parrot", parrot.name
     assert_equal "green", parrot.color
 
     same_parrot = Bird.where(color: "green").first_or_create(name: "parakeet")
     assert_kind_of Bird, same_parrot
-    assert same_parrot.persisted?
+    assert_predicate same_parrot, :persisted?
     assert_equal parrot, same_parrot
   end
 
   def test_first_or_create_with_no_parameters
     parrot = Bird.where(color: "green").first_or_create
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
+    assert_not_predicate parrot, :persisted?
     assert_equal "green", parrot.color
   end
 
   def test_first_or_create_with_block
     parrot = Bird.where(color: "green").first_or_create { |bird| bird.name = "parrot" }
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "green", parrot.color
     assert_equal "parrot", parrot.name
 
@@ -1242,13 +1249,13 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_create_bang_with_valid_options
     parrot = Bird.where(color: "green").first_or_create!(name: "parrot")
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "parrot", parrot.name
     assert_equal "green", parrot.color
 
     same_parrot = Bird.where(color: "green").first_or_create!(name: "parakeet")
     assert_kind_of Bird, same_parrot
-    assert same_parrot.persisted?
+    assert_predicate same_parrot, :persisted?
     assert_equal parrot, same_parrot
   end
 
@@ -1263,7 +1270,7 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_create_bang_with_valid_block
     parrot = Bird.where(color: "green").first_or_create! { |bird| bird.name = "parrot" }
     assert_kind_of Bird, parrot
-    assert parrot.persisted?
+    assert_predicate parrot, :persisted?
     assert_equal "green", parrot.color
     assert_equal "parrot", parrot.name
 
@@ -1294,9 +1301,9 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_initialize
     parrot = Bird.where(color: "green").first_or_initialize(name: "parrot")
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
-    assert parrot.valid?
-    assert parrot.new_record?
+    assert_not_predicate parrot, :persisted?
+    assert_predicate parrot, :valid?
+    assert_predicate parrot, :new_record?
     assert_equal "parrot", parrot.name
     assert_equal "green", parrot.color
   end
@@ -1304,18 +1311,18 @@ class RelationTest < ActiveRecord::TestCase
   def test_first_or_initialize_with_no_parameters
     parrot = Bird.where(color: "green").first_or_initialize
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
-    assert !parrot.valid?
-    assert parrot.new_record?
+    assert_not_predicate parrot, :persisted?
+    assert_not_predicate parrot, :valid?
+    assert_predicate parrot, :new_record?
     assert_equal "green", parrot.color
   end
 
   def test_first_or_initialize_with_block
     parrot = Bird.where(color: "green").first_or_initialize { |bird| bird.name = "parrot" }
     assert_kind_of Bird, parrot
-    assert !parrot.persisted?
-    assert parrot.valid?
-    assert parrot.new_record?
+    assert_not_predicate parrot, :persisted?
+    assert_predicate parrot, :valid?
+    assert_predicate parrot, :new_record?
     assert_equal "green", parrot.color
     assert_equal "parrot", parrot.name
   end
@@ -1324,7 +1331,7 @@ class RelationTest < ActiveRecord::TestCase
     assert_nil Bird.find_by(name: "bob")
 
     bird = Bird.find_or_create_by(name: "bob")
-    assert bird.persisted?
+    assert_predicate bird, :persisted?
 
     assert_equal bird, Bird.find_or_create_by(name: "bob")
   end
@@ -1333,7 +1340,7 @@ class RelationTest < ActiveRecord::TestCase
     assert_nil Bird.find_by(name: "bob")
 
     bird = Bird.create_with(color: "green").find_or_create_by(name: "bob")
-    assert bird.persisted?
+    assert_predicate bird, :persisted?
     assert_equal "green", bird.color
 
     assert_equal bird, Bird.create_with(color: "blue").find_or_create_by(name: "bob")
@@ -1343,11 +1350,39 @@ class RelationTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::RecordInvalid) { Bird.find_or_create_by!(color: "green") }
   end
 
+  def test_create_or_find_by
+    assert_nil Subscriber.find_by(nick: "bob")
+
+    subscriber = Subscriber.create!(nick: "bob")
+
+    assert_equal subscriber, Subscriber.create_or_find_by(nick: "bob")
+    assert_not_equal subscriber, Subscriber.create_or_find_by(nick: "cat")
+  end
+
+  def test_create_or_find_by_with_non_unique_attributes
+    Subscriber.create!(nick: "bob", name: "the builder")
+
+    assert_raises(ActiveRecord::RecordNotFound) do
+      Subscriber.create_or_find_by(nick: "bob", name: "the cat")
+    end
+  end
+
+  def test_create_or_find_by_within_transaction
+    assert_nil Subscriber.find_by(nick: "bob")
+
+    subscriber = Subscriber.create!(nick: "bob")
+
+    Subscriber.transaction do
+      assert_equal subscriber, Subscriber.create_or_find_by(nick: "bob")
+      assert_not_equal subscriber, Subscriber.create_or_find_by(nick: "cat")
+    end
+  end
+
   def test_find_or_initialize_by
     assert_nil Bird.find_by(name: "bob")
 
     bird = Bird.find_or_initialize_by(name: "bob")
-    assert bird.new_record?
+    assert_predicate bird, :new_record?
     bird.save!
 
     assert_equal bird, Bird.find_or_initialize_by(name: "bob")
@@ -1522,10 +1557,10 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_doesnt_add_having_values_if_options_are_blank
     scope = Post.having("")
-    assert scope.having_clause.empty?
+    assert_empty scope.having_clause
 
     scope = Post.having([])
-    assert scope.having_clause.empty?
+    assert_empty scope.having_clause
   end
 
   def test_having_with_binds_for_both_where_and_having
@@ -1551,13 +1586,13 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_references_triggers_eager_loading
     scope = Post.includes(:comments)
-    assert !scope.eager_loading?
-    assert scope.references(:comments).eager_loading?
+    assert_not_predicate scope, :eager_loading?
+    assert_predicate scope.references(:comments), :eager_loading?
   end
 
   def test_references_doesnt_trigger_eager_loading_if_reference_not_included
     scope = Post.references(:comments)
-    assert !scope.eager_loading?
+    assert_not_predicate scope, :eager_loading?
   end
 
   def test_automatically_added_where_references
@@ -1665,7 +1700,7 @@ class RelationTest < ActiveRecord::TestCase
     # count always trigger the COUNT query.
     assert_queries(1) { topics.count }
 
-    assert topics.loaded?
+    assert_predicate topics, :loaded?
   end
 
   test "find_by with hash conditions returns the first matching record" do
@@ -1840,7 +1875,7 @@ class RelationTest < ActiveRecord::TestCase
   test "delegations do not leak to other classes" do
     Topic.all.by_lifo
     assert Topic.all.class.method_defined?(:by_lifo)
-    assert !Post.all.respond_to?(:by_lifo)
+    assert_not_respond_to Post.all, :by_lifo
   end
 
   def test_unscope_with_subquery
@@ -1865,7 +1900,7 @@ class RelationTest < ActiveRecord::TestCase
 
   def test_locked_should_not_build_arel
     posts = Post.locked
-    assert posts.locked?
+    assert_predicate posts, :locked?
     assert_nothing_raised { posts.lock!(false) }
   end
 
@@ -1934,6 +1969,10 @@ class RelationTest < ActiveRecord::TestCase
       table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
       predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
 
-      ActiveRecord::Relation.create(Post, table_alias, predicate_builder)
+      ActiveRecord::Relation.create(
+        Post,
+        table: table_alias,
+        predicate_builder: predicate_builder
+      )
     end
 end
diff --git a/activerecord/test/cases/reserved_word_test.rb b/activerecord/test/cases/reserved_word_test.rb
index 4f8ca392b9..e32605fd11 100644
--- a/activerecord/test/cases/reserved_word_test.rb
+++ b/activerecord/test/cases/reserved_word_test.rb
@@ -116,7 +116,7 @@ class ReservedWordTest < ActiveRecord::TestCase
   end
 
   def test_activerecord_introspection
-    assert Group.table_exists?
+    assert_predicate Group, :table_exists?
     assert_equal ["id", "order", "select_id"], Group.columns.map(&:name).sort
   end
 
diff --git a/activerecord/test/cases/sanitize_test.rb b/activerecord/test/cases/sanitize_test.rb
index 1b0605e369..778cf86ac3 100644
--- a/activerecord/test/cases/sanitize_test.rb
+++ b/activerecord/test/cases/sanitize_test.rb
@@ -4,6 +4,7 @@ require "cases/helper"
 require "models/binary"
 require "models/author"
 require "models/post"
+require "models/customer"
 
 class SanitizeTest < ActiveRecord::TestCase
   def setup
@@ -167,6 +168,12 @@ class SanitizeTest < ActiveRecord::TestCase
     assert_equal "#{ActiveRecord::Base.connection.quote('10')}::integer '2009-01-01'::date", l.call
   end
 
+  def test_deprecated_expand_hash_conditions_for_aggregates
+    assert_deprecated do
+      assert_equal({ "balance" => 50 }, Customer.send(:expand_hash_conditions_for_aggregates, balance: Money.new(50)))
+    end
+  end
+
   private
     def bind(statement, *vars)
       if vars.first.is_a?(Hash)
diff --git a/activerecord/test/cases/scoping/default_scoping_test.rb b/activerecord/test/cases/scoping/default_scoping_test.rb
index 6ff0f93cf3..0804de1fb3 100644
--- a/activerecord/test/cases/scoping/default_scoping_test.rb
+++ b/activerecord/test/cases/scoping/default_scoping_test.rb
@@ -302,8 +302,8 @@ class DefaultScopingTest < ActiveRecord::TestCase
 
   def test_unscope_merging
     merged = Developer.where(name: "Jamis").merge(Developer.unscope(:where))
-    assert merged.where_clause.empty?
-    assert !merged.where(name: "Jon").where_clause.empty?
+    assert_empty merged.where_clause
+    assert_not_empty merged.where(name: "Jon").where_clause
   end
 
   def test_order_in_default_scope_should_not_prevail
diff --git a/activerecord/test/cases/scoping/named_scoping_test.rb b/activerecord/test/cases/scoping/named_scoping_test.rb
index 17d3f27bb1..ea71a5ce28 100644
--- a/activerecord/test/cases/scoping/named_scoping_test.rb
+++ b/activerecord/test/cases/scoping/named_scoping_test.rb
@@ -13,7 +13,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   fixtures :posts, :authors, :topics, :comments, :author_addresses
 
   def test_implements_enumerable
-    assert !Topic.all.empty?
+    assert_not_empty Topic.all
 
     assert_equal Topic.all.to_a, Topic.base
     assert_equal Topic.all.to_a, Topic.base.to_a
@@ -40,7 +40,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_delegates_finds_and_calculations_to_the_base_class
-    assert !Topic.all.empty?
+    assert_not_empty Topic.all
 
     assert_equal Topic.all.to_a,                Topic.base.to_a
     assert_equal Topic.first,                   Topic.base.first
@@ -65,13 +65,13 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_scope_should_respond_to_own_methods_and_methods_of_the_proxy
-    assert Topic.approved.respond_to?(:limit)
-    assert Topic.approved.respond_to?(:count)
-    assert Topic.approved.respond_to?(:length)
+    assert_respond_to Topic.approved, :limit
+    assert_respond_to Topic.approved, :count
+    assert_respond_to Topic.approved, :length
   end
 
   def test_scopes_with_options_limit_finds_to_those_matching_the_criteria_specified
-    assert !Topic.all.merge!(where: { approved: true }).to_a.empty?
+    assert_not_empty Topic.all.merge!(where: { approved: true }).to_a
 
     assert_equal Topic.all.merge!(where: { approved: true }).to_a, Topic.approved
     assert_equal Topic.where(approved: true).count, Topic.approved.count
@@ -87,7 +87,7 @@ class NamedScopingTest < ActiveRecord::TestCase
     assert_equal((approved = Topic.all.merge!(where: { approved: true }).to_a), Topic.approved)
     assert_equal((replied = Topic.all.merge!(where: "replies_count > 0").to_a), Topic.replied)
     assert !(approved == replied)
-    assert !(approved & replied).empty?
+    assert_not_empty (approved & replied)
 
     assert_equal approved & replied, Topic.approved.replied
   end
@@ -115,7 +115,7 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_has_many_associations_have_access_to_scopes
     assert_not_equal Post.containing_the_letter_a, authors(:david).posts
-    assert !Post.containing_the_letter_a.empty?
+    assert_not_empty Post.containing_the_letter_a
 
     expected = authors(:david).posts & Post.containing_the_letter_a
     assert_equal expected.sort_by(&:id), authors(:david).posts.containing_the_letter_a.sort_by(&:id)
@@ -128,15 +128,15 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_has_many_through_associations_have_access_to_scopes
     assert_not_equal Comment.containing_the_letter_e, authors(:david).comments
-    assert !Comment.containing_the_letter_e.empty?
+    assert_not_empty Comment.containing_the_letter_e
 
     expected = authors(:david).comments & Comment.containing_the_letter_e
     assert_equal expected.sort_by(&:id), authors(:david).comments.containing_the_letter_e.sort_by(&:id)
   end
 
   def test_scopes_honor_current_scopes_from_when_defined
-    assert !Post.ranked_by_comments.limit_by(5).empty?
-    assert !authors(:david).posts.ranked_by_comments.limit_by(5).empty?
+    assert_not_empty Post.ranked_by_comments.limit_by(5)
+    assert_not_empty authors(:david).posts.ranked_by_comments.limit_by(5)
     assert_not_equal Post.ranked_by_comments.limit_by(5), authors(:david).posts.ranked_by_comments.limit_by(5)
     assert_not_equal Post.top(5), authors(:david).posts.top(5)
     # Oracle sometimes sorts differently if WHERE condition is changed
@@ -168,14 +168,14 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_active_records_have_scope_named__all__
-    assert !Topic.all.empty?
+    assert_not_empty Topic.all
 
     assert_equal Topic.all.to_a, Topic.base
   end
 
   def test_active_records_have_scope_named__scoped__
     scope = Topic.where("content LIKE '%Have%'")
-    assert !scope.empty?
+    assert_not_empty scope
 
     assert_equal scope, Topic.all.merge!(where: "content LIKE '%Have%'")
   end
@@ -228,9 +228,9 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_model_class_should_respond_to_any
-    assert Topic.any?
+    assert_predicate Topic, :any?
     Topic.delete_all
-    assert !Topic.any?
+    assert_not_predicate Topic, :any?
   end
 
   def test_many_should_not_load_results
@@ -259,22 +259,22 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_many_should_return_false_if_none_or_one
     topics = Topic.base.where(id: 0)
-    assert !topics.many?
+    assert_not_predicate topics, :many?
     topics = Topic.base.where(id: 1)
-    assert !topics.many?
+    assert_not_predicate topics, :many?
   end
 
   def test_many_should_return_true_if_more_than_one
-    assert Topic.base.many?
+    assert_predicate Topic.base, :many?
   end
 
   def test_model_class_should_respond_to_many
     Topic.delete_all
-    assert !Topic.many?
+    assert_not_predicate Topic, :many?
     Topic.create!
-    assert !Topic.many?
+    assert_not_predicate Topic, :many?
     Topic.create!
-    assert Topic.many?
+    assert_predicate Topic, :many?
   end
 
   def test_should_build_on_top_of_scope
@@ -423,16 +423,16 @@ class NamedScopingTest < ActiveRecord::TestCase
 
   def test_chaining_applies_last_conditions_when_creating
     post = Topic.rejected.new
-    assert !post.approved?
+    assert_not_predicate post, :approved?
 
     post = Topic.rejected.approved.new
-    assert post.approved?
+    assert_predicate post, :approved?
 
     post = Topic.approved.rejected.new
-    assert !post.approved?
+    assert_not_predicate post, :approved?
 
     post = Topic.approved.rejected.approved.new
-    assert post.approved?
+    assert_predicate post, :approved?
   end
 
   def test_chaining_combines_conditions_when_searching
@@ -498,7 +498,7 @@ class NamedScopingTest < ActiveRecord::TestCase
   def test_index_on_scope
     approved = Topic.approved.order("id ASC")
     assert_equal topics(:second), approved[0]
-    assert approved.loaded?
+    assert_predicate approved, :loaded?
   end
 
   def test_nested_scopes_queries_size
@@ -578,16 +578,16 @@ class NamedScopingTest < ActiveRecord::TestCase
   end
 
   def test_model_class_should_respond_to_none
-    assert !Topic.none?
+    assert_not_predicate Topic, :none?
     Topic.delete_all
-    assert Topic.none?
+    assert_predicate Topic, :none?
   end
 
   def test_model_class_should_respond_to_one
-    assert !Topic.one?
+    assert_not_predicate Topic, :one?
     Topic.delete_all
-    assert !Topic.one?
+    assert_not_predicate Topic, :one?
     Topic.create!
-    assert Topic.one?
+    assert_predicate Topic, :one?
   end
 end
diff --git a/activerecord/test/cases/scoping/relation_scoping_test.rb b/activerecord/test/cases/scoping/relation_scoping_test.rb
index 116f8e83aa..5c86bc892d 100644
--- a/activerecord/test/cases/scoping/relation_scoping_test.rb
+++ b/activerecord/test/cases/scoping/relation_scoping_test.rb
@@ -213,21 +213,21 @@ class RelationScopingTest < ActiveRecord::TestCase
 
   def test_current_scope_does_not_pollute_sibling_subclasses
     Comment.none.scoping do
-      assert_not SpecialComment.all.any?
-      assert_not VerySpecialComment.all.any?
-      assert_not SubSpecialComment.all.any?
+      assert_not_predicate SpecialComment.all, :any?
+      assert_not_predicate VerySpecialComment.all, :any?
+      assert_not_predicate SubSpecialComment.all, :any?
     end
 
     SpecialComment.none.scoping do
-      assert Comment.all.any?
-      assert VerySpecialComment.all.any?
-      assert_not SubSpecialComment.all.any?
+      assert_predicate Comment.all, :any?
+      assert_predicate VerySpecialComment.all, :any?
+      assert_not_predicate SubSpecialComment.all, :any?
     end
 
     SubSpecialComment.none.scoping do
-      assert Comment.all.any?
-      assert VerySpecialComment.all.any?
-      assert SpecialComment.all.any?
+      assert_predicate Comment.all, :any?
+      assert_predicate VerySpecialComment.all, :any?
+      assert_predicate SpecialComment.all, :any?
     end
   end
 
@@ -334,7 +334,7 @@ class NestedRelationScopingTest < ActiveRecord::TestCase
   def test_nested_exclusive_scope_for_create
     comment = Comment.create_with(body: "Hey guys, nested scopes are broken. Please fix!").scoping do
       Comment.unscoped.create_with(post_id: 1).scoping do
-        assert Comment.new.body.blank?
+        assert_predicate Comment.new.body, :blank?
         Comment.create body: "Hey guys"
       end
     end
diff --git a/activerecord/test/cases/serialized_attribute_test.rb b/activerecord/test/cases/serialized_attribute_test.rb
index 32dafbd458..7de5429cbb 100644
--- a/activerecord/test/cases/serialized_attribute_test.rb
+++ b/activerecord/test/cases/serialized_attribute_test.rb
@@ -279,7 +279,7 @@ class SerializedAttributeTest < ActiveRecord::TestCase
 
     topic = Topic.new(content: nil)
 
-    assert_not topic.content_changed?
+    assert_not_predicate topic, :content_changed?
   end
 
   def test_classes_without_no_arg_constructors_are_not_supported
@@ -349,7 +349,7 @@ class SerializedAttributeTest < ActiveRecord::TestCase
 
     topic = model.create!(foo: "bar")
     topic.foo
-    refute topic.changed?
+    assert_not_predicate topic, :changed?
   end
 
   def test_serialized_attribute_works_under_concurrent_initial_access
diff --git a/activerecord/test/cases/store_test.rb b/activerecord/test/cases/store_test.rb
index ebf4016960..a30d13632a 100644
--- a/activerecord/test/cases/store_test.rb
+++ b/activerecord/test/cases/store_test.rb
@@ -45,7 +45,7 @@ class StoreTest < ActiveRecord::TestCase
 
   test "updating the store will mark it as changed" do
     @john.color = "red"
-    assert @john.settings_changed?
+    assert_predicate @john, :settings_changed?
   end
 
   test "updating the store populates the changed array correctly" do
@@ -56,7 +56,7 @@ class StoreTest < ActiveRecord::TestCase
 
   test "updating the store won't mark it as changed if an attribute isn't changed" do
     @john.color = @john.color
-    assert !@john.settings_changed?
+    assert_not_predicate @john, :settings_changed?
   end
 
   test "object initialization with not nullable column" do
@@ -137,7 +137,7 @@ class StoreTest < ActiveRecord::TestCase
 
   test "updating the store will mark it as changed encoded with JSON" do
     @john.height = "short"
-    assert @john.json_data_changed?
+    assert_predicate @john, :json_data_changed?
   end
 
   test "object initialization with not nullable column encoded with JSON" do
diff --git a/activerecord/test/cases/tasks/database_tasks_test.rb b/activerecord/test/cases/tasks/database_tasks_test.rb
index c114842dec..21226352ff 100644
--- a/activerecord/test/cases/tasks/database_tasks_test.rb
+++ b/activerecord/test/cases/tasks/database_tasks_test.rb
@@ -28,10 +28,10 @@ module ActiveRecord
 
   class DatabaseTasksUtilsTask < ActiveRecord::TestCase
     def test_raises_an_error_when_called_with_protected_environment
-      ActiveRecord::Migrator.stubs(:current_version).returns(1)
+      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
 
       protected_environments = ActiveRecord::Base.protected_environments
-      current_env            = ActiveRecord::Migrator.current_environment
+      current_env            = ActiveRecord::Base.connection.migration_context.current_environment
       assert_not_includes protected_environments, current_env
       # Assert no error
       ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
@@ -45,10 +45,10 @@ module ActiveRecord
     end
 
     def test_raises_an_error_when_called_with_protected_environment_which_name_is_a_symbol
-      ActiveRecord::Migrator.stubs(:current_version).returns(1)
+      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
 
       protected_environments = ActiveRecord::Base.protected_environments
-      current_env            = ActiveRecord::Migrator.current_environment
+      current_env            = ActiveRecord::Base.connection.migration_context.current_environment
       assert_not_includes protected_environments, current_env
       # Assert no error
       ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
@@ -63,7 +63,7 @@ module ActiveRecord
 
     def test_raises_an_error_if_no_migrations_have_been_made
       ActiveRecord::InternalMetadata.stubs(:table_exists?).returns(false)
-      ActiveRecord::Migrator.stubs(:current_version).returns(1)
+      ActiveRecord::MigrationContext.any_instance.stubs(:current_version).returns(1)
 
       assert_raise(ActiveRecord::NoEnvironmentInSchemaError) do
         ActiveRecord::Tasks::DatabaseTasks.check_protected_environments!
@@ -347,50 +347,92 @@ module ActiveRecord
     end
   end
 
-  class DatabaseTasksMigrateTest < ActiveRecord::TestCase
-    self.use_transactional_tests = false
+  if current_adapter?(:SQLite3Adapter) && !in_memory_db?
+    class DatabaseTasksMigrateTest < ActiveRecord::TestCase
+      self.use_transactional_tests = false
+
+      # Use a memory db here to avoid having to rollback at the end
+      setup do
+        migrations_path = MIGRATIONS_ROOT + "/valid"
+        file = ActiveRecord::Base.connection.raw_connection.filename
+        @conn = ActiveRecord::Base.establish_connection adapter: "sqlite3",
+          database: ":memory:", migrations_paths: migrations_path
+        source_db = SQLite3::Database.new file
+        dest_db = ActiveRecord::Base.connection.raw_connection
+        backup = SQLite3::Backup.new(dest_db, "main", source_db, "main")
+        backup.step(-1)
+        backup.finish
+      end
 
-    def setup
-      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = "custom/path"
-    end
+      teardown do
+        @conn.release_connection if @conn
+        ActiveRecord::Base.establish_connection :arunit
+      end
 
-    def teardown
-      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = nil
-    end
+      def test_migrate_set_and_unset_verbose_and_version_env_vars
+        verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+        ENV["VERSION"] = "2"
+        ENV["VERBOSE"] = "false"
 
-    def test_migrate_receives_correct_env_vars
-      verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+        # run down migration because it was already run on copied db
+        assert_empty capture_migration_output
 
-      ENV["VERBOSE"] = "false"
-      ENV["VERSION"] = "4"
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", 4)
-      ActiveRecord::Migration.expects(:verbose=).with(false)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+        ENV.delete("VERSION")
+        ENV.delete("VERBOSE")
 
-      ENV.delete("VERBOSE")
-      ENV.delete("VERSION")
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", nil)
-      ActiveRecord::Migration.expects(:verbose=).with(true)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+        # re-run up migration
+        assert_includes capture_migration_output, "migrating"
+      ensure
+        ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      end
 
-      ENV["VERBOSE"] = ""
-      ENV["VERSION"] = ""
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", nil)
-      ActiveRecord::Migration.expects(:verbose=).with(true)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
+      def test_migrate_set_and_unset_empty_values_for_verbose_and_version_env_vars
+        verbose, version = ENV["VERBOSE"], ENV["VERSION"]
 
-      ENV["VERBOSE"] = "yes"
-      ENV["VERSION"] = "0"
-      ActiveRecord::Migrator.expects(:migrate).with("custom/path", 0)
-      ActiveRecord::Migration.expects(:verbose=).with(true)
-      ActiveRecord::Migration.expects(:verbose=).with(ActiveRecord::Migration.verbose)
-      ActiveRecord::Tasks::DatabaseTasks.migrate
-    ensure
-      ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+        ENV["VERSION"] = "2"
+        ENV["VERBOSE"] = "false"
+
+        # run down migration because it was already run on copied db
+        assert_empty capture_migration_output
+
+        ENV["VERBOSE"] = ""
+        ENV["VERSION"] = ""
+
+        # re-run up migration
+        assert_includes capture_migration_output, "migrating"
+      ensure
+        ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      end
+
+      def test_migrate_set_and_unset_nonsense_values_for_verbose_and_version_env_vars
+        verbose, version = ENV["VERBOSE"], ENV["VERSION"]
+
+        # run down migration because it was already run on copied db
+        ENV["VERSION"] = "2"
+        ENV["VERBOSE"] = "false"
+
+        assert_empty capture_migration_output
+
+        ENV["VERBOSE"] = "yes"
+        ENV["VERSION"] = "2"
+
+        # run no migration because 2 was already run
+        assert_empty capture_migration_output
+      ensure
+        ENV["VERBOSE"], ENV["VERSION"] = verbose, version
+      end
+
+      private
+        def capture_migration_output
+          capture(:stdout) do
+            ActiveRecord::Tasks::DatabaseTasks.migrate
+          end
+        end
     end
+  end
+
+  class DatabaseTasksMigrateErrorTest < ActiveRecord::TestCase
+    self.use_transactional_tests = false
 
     def test_migrate_raise_error_on_invalid_version_format
       version = ENV["VERSION"]
diff --git a/activerecord/test/cases/timestamp_test.rb b/activerecord/test/cases/timestamp_test.rb
index 54e3f47e16..e95446c0a7 100644
--- a/activerecord/test/cases/timestamp_test.rb
+++ b/activerecord/test/cases/timestamp_test.rb
@@ -139,13 +139,13 @@ class TimestampTest < ActiveRecord::TestCase
 
   def test_touching_a_no_touching_object
     Developer.no_touching do
-      assert @developer.no_touching?
-      assert !@owner.no_touching?
+      assert_predicate @developer, :no_touching?
+      assert_not_predicate @owner, :no_touching?
       @developer.touch
     end
 
-    assert !@developer.no_touching?
-    assert !@owner.no_touching?
+    assert_not_predicate @developer, :no_touching?
+    assert_not_predicate @owner, :no_touching?
     assert_equal @previously_updated_at, @developer.updated_at
   end
 
@@ -162,26 +162,26 @@ class TimestampTest < ActiveRecord::TestCase
 
   def test_global_no_touching
     ActiveRecord::Base.no_touching do
-      assert @developer.no_touching?
-      assert @owner.no_touching?
+      assert_predicate @developer, :no_touching?
+      assert_predicate @owner, :no_touching?
       @developer.touch
     end
 
-    assert !@developer.no_touching?
-    assert !@owner.no_touching?
+    assert_not_predicate @developer, :no_touching?
+    assert_not_predicate @owner, :no_touching?
     assert_equal @previously_updated_at, @developer.updated_at
   end
 
   def test_no_touching_threadsafe
     Thread.new do
       Developer.no_touching do
-        assert @developer.no_touching?
+        assert_predicate @developer, :no_touching?
 
         sleep(1)
       end
     end
 
-    assert !@developer.no_touching?
+    assert_not_predicate @developer, :no_touching?
   end
 
   def test_no_touching_with_callbacks
@@ -237,7 +237,7 @@ class TimestampTest < ActiveRecord::TestCase
     pet = Pet.new(owner: klass.new)
     pet.save!
 
-    assert pet.owner.new_record?
+    assert_predicate pet.owner, :new_record?
   end
 
   def test_saving_a_record_with_a_belongs_to_that_specifies_touching_a_specific_attribute_the_parent_should_update_that_attribute
diff --git a/activerecord/test/cases/touch_later_test.rb b/activerecord/test/cases/touch_later_test.rb
index 1757031371..925a4609a2 100644
--- a/activerecord/test/cases/touch_later_test.rb
+++ b/activerecord/test/cases/touch_later_test.rb
@@ -13,7 +13,7 @@ class TouchLaterTest < ActiveRecord::TestCase
   def test_touch_laster_raise_if_non_persisted
     invoice = Invoice.new
     Invoice.transaction do
-      assert_not invoice.persisted?
+      assert_not_predicate invoice, :persisted?
       assert_raises(ActiveRecord::ActiveRecordError) do
         invoice.touch_later
       end
@@ -23,7 +23,7 @@ class TouchLaterTest < ActiveRecord::TestCase
   def test_touch_later_dont_set_dirty_attributes
     invoice = Invoice.create!
     invoice.touch_later
-    assert_not invoice.changed?
+    assert_not_predicate invoice, :changed?
   end
 
   def test_touch_later_respects_no_touching_policy
diff --git a/activerecord/test/cases/transaction_callbacks_test.rb b/activerecord/test/cases/transaction_callbacks_test.rb
index 1f370a80ee..1c7cec4dad 100644
--- a/activerecord/test/cases/transaction_callbacks_test.rb
+++ b/activerecord/test/cases/transaction_callbacks_test.rb
@@ -158,13 +158,13 @@ class TransactionCallbacksTest < ActiveRecord::TestCase
 
   def test_only_call_after_commit_on_top_level_transactions
     @first.after_commit_block { |r| r.history << :after_commit }
-    assert @first.history.empty?
+    assert_empty @first.history
 
     @first.transaction do
       @first.transaction(requires_new: true) do
         @first.touch
       end
-      assert @first.history.empty?
+      assert_empty @first.history
     end
     assert_equal [:after_commit], @first.history
   end
@@ -518,7 +518,7 @@ class TransactionEnrollmentCallbacksTest < ActiveRecord::TestCase
       @topic.content = "foo"
       @topic.save!
     end
-    assert @topic.history.empty?
+    assert_empty @topic.history
   end
 
   def test_commit_run_transactions_callbacks_with_explicit_enrollment
@@ -538,7 +538,7 @@ class TransactionEnrollmentCallbacksTest < ActiveRecord::TestCase
       @topic.save!
       raise ActiveRecord::Rollback
     end
-    assert @topic.history.empty?
+    assert_empty @topic.history
   end
 
   def test_rollback_run_transactions_callbacks_with_explicit_enrollment
diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index c110fa2f7d..c70286d52a 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -20,22 +20,22 @@ class TransactionTest < ActiveRecord::TestCase
 
   def test_persisted_in_a_model_with_custom_primary_key_after_failed_save
     movie = Movie.create
-    assert !movie.persisted?
+    assert_not_predicate movie, :persisted?
   end
 
   def test_raise_after_destroy
-    assert_not @first.frozen?
+    assert_not_predicate @first, :frozen?
 
     assert_raises(RuntimeError) {
       Topic.transaction do
         @first.destroy
-        assert @first.frozen?
+        assert_predicate @first, :frozen?
         raise
       end
     }
 
     assert @first.reload
-    assert_not @first.frozen?
+    assert_not_predicate @first, :frozen?
   end
 
   def test_successful
@@ -152,7 +152,7 @@ class TransactionTest < ActiveRecord::TestCase
     @first.approved = true
     e = assert_raises(RuntimeError) { @first.save }
     assert_equal "Make the transaction rollback", e.message
-    assert !Topic.find(1).approved?
+    assert_not_predicate Topic.find(1), :approved?
   end
 
   def test_rolling_back_in_a_callback_rollbacks_before_save
@@ -186,7 +186,7 @@ class TransactionTest < ActiveRecord::TestCase
     author = Author.create! name: "foo"
     author.name = nil
     assert_not author.save
-    assert_not author.new_record?
+    assert_not_predicate author, :new_record?
   end
 
   def test_update_should_rollback_on_failure
@@ -417,8 +417,8 @@ class TransactionTest < ActiveRecord::TestCase
       end
     end
 
-    assert @first.reload.approved?
-    assert !@second.reload.approved?
+    assert_predicate @first.reload, :approved?
+    assert_not_predicate @second.reload, :approved?
   end if Topic.connection.supports_savepoints?
 
   def test_force_savepoint_on_instance
@@ -438,8 +438,8 @@ class TransactionTest < ActiveRecord::TestCase
       end
     end
 
-    assert @first.reload.approved?
-    assert !@second.reload.approved?
+    assert_predicate @first.reload, :approved?
+    assert_not_predicate @second.reload, :approved?
   end if Topic.connection.supports_savepoints?
 
   def test_no_savepoint_in_nested_transaction_without_force
@@ -459,8 +459,8 @@ class TransactionTest < ActiveRecord::TestCase
       end
     end
 
-    assert !@first.reload.approved?
-    assert !@second.reload.approved?
+    assert_not_predicate @first.reload, :approved?
+    assert_not_predicate @second.reload, :approved?
   end if Topic.connection.supports_savepoints?
 
   def test_many_savepoints
@@ -516,12 +516,12 @@ class TransactionTest < ActiveRecord::TestCase
       @first.approved = false
       @first.save!
       Topic.connection.rollback_to_savepoint("first")
-      assert @first.reload.approved?
+      assert_predicate @first.reload, :approved?
 
       @first.approved = false
       @first.save!
       Topic.connection.release_savepoint("first")
-      assert_not @first.reload.approved?
+      assert_not_predicate @first.reload, :approved?
     end
   end if Topic.connection.supports_savepoints?
 
@@ -663,8 +663,8 @@ class TransactionTest < ActiveRecord::TestCase
       raise ActiveRecord::Rollback
     end
 
-    assert_not reply.frozen?
-    assert_not topic.frozen?
+    assert_not_predicate reply, :frozen?
+    assert_not_predicate topic, :frozen?
   end
 
   def test_restore_id_after_rollback
@@ -819,28 +819,28 @@ class TransactionTest < ActiveRecord::TestCase
     connection = Topic.connection
     transaction = ActiveRecord::ConnectionAdapters::TransactionManager.new(connection).begin_transaction
 
-    assert transaction.open?
-    assert !transaction.state.rolledback?
-    assert !transaction.state.committed?
+    assert_predicate transaction, :open?
+    assert_not_predicate transaction.state, :rolledback?
+    assert_not_predicate transaction.state, :committed?
 
     transaction.rollback
 
-    assert transaction.state.rolledback?
-    assert !transaction.state.committed?
+    assert_predicate transaction.state, :rolledback?
+    assert_not_predicate transaction.state, :committed?
   end
 
   def test_transactions_state_from_commit
     connection = Topic.connection
     transaction = ActiveRecord::ConnectionAdapters::TransactionManager.new(connection).begin_transaction
 
-    assert transaction.open?
-    assert !transaction.state.rolledback?
-    assert !transaction.state.committed?
+    assert_predicate transaction, :open?
+    assert_not_predicate transaction.state, :rolledback?
+    assert_not_predicate transaction.state, :committed?
 
     transaction.commit
 
-    assert !transaction.state.rolledback?
-    assert transaction.state.committed?
+    assert_not_predicate transaction.state, :rolledback?
+    assert_predicate transaction.state, :committed?
   end
 
   def test_set_state_method_is_deprecated
@@ -929,7 +929,7 @@ class TransactionsWithTransactionalFixturesTest < ActiveRecord::TestCase
         raise
       end
     rescue
-      assert !@first.reload.approved?
+      assert_not_predicate @first.reload, :approved?
     end
   end
 
@@ -950,7 +950,7 @@ class TransactionsWithTransactionalFixturesTest < ActiveRecord::TestCase
       end
     end
 
-    assert !@first.reload.approved?
+    assert_not_predicate @first.reload, :approved?
   end
 end if Topic.connection.supports_savepoints?
 
diff --git a/activerecord/test/cases/type/string_test.rb b/activerecord/test/cases/type/string_test.rb
index 8c51b30fdd..9e7810a6a5 100644
--- a/activerecord/test/cases/type/string_test.rb
+++ b/activerecord/test/cases/type/string_test.rb
@@ -9,16 +9,16 @@ module ActiveRecord
       klass.table_name = "authors"
 
       author = klass.create!(name: "Sean")
-      assert_not author.changed?
+      assert_not_predicate author, :changed?
 
       author.name << " Griffin"
-      assert author.name_changed?
+      assert_predicate author, :name_changed?
 
       author.save!
       author.reload
 
       assert_equal "Sean Griffin", author.name
-      assert_not author.changed?
+      assert_not_predicate author, :changed?
     end
   end
 end
diff --git a/activerecord/test/cases/validations/absence_validation_test.rb b/activerecord/test/cases/validations/absence_validation_test.rb
index a997f8be9c..8235a54d8a 100644
--- a/activerecord/test/cases/validations/absence_validation_test.rb
+++ b/activerecord/test/cases/validations/absence_validation_test.rb
@@ -13,8 +13,8 @@ class AbsenceValidationTest < ActiveRecord::TestCase
       validates_absence_of :name
     end
 
-    assert boy_klass.new.valid?
-    assert_not boy_klass.new(name: "Alex").valid?
+    assert_predicate boy_klass.new, :valid?
+    assert_not_predicate boy_klass.new(name: "Alex"), :valid?
   end
 
   def test_has_one_marked_for_destruction
@@ -44,7 +44,7 @@ class AbsenceValidationTest < ActiveRecord::TestCase
     assert_not boy.valid?, "should not be valid if has_many association is present"
 
     i2.mark_for_destruction
-    assert boy.valid?
+    assert_predicate boy, :valid?
   end
 
   def test_does_not_call_to_a_on_associations
@@ -65,11 +65,11 @@ class AbsenceValidationTest < ActiveRecord::TestCase
       Interest.validates_absence_of(:token)
 
       interest = Interest.create!(topic: "Thought Leadering")
-      assert interest.valid?
+      assert_predicate interest, :valid?
 
       interest.token = "tl"
 
-      assert interest.invalid?
+      assert_predicate interest, :invalid?
     end
   end
 end
diff --git a/activerecord/test/cases/validations/association_validation_test.rb b/activerecord/test/cases/validations/association_validation_test.rb
index 80fe375ae5..ce6d42b34b 100644
--- a/activerecord/test/cases/validations/association_validation_test.rb
+++ b/activerecord/test/cases/validations/association_validation_test.rb
@@ -16,14 +16,14 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Reply.validates_presence_of(:content)
     t = Topic.create("title" => "uhohuhoh", "content" => "whatever")
     t.replies << [r = Reply.new("title" => "A reply"), r2 = Reply.new("title" => "Another reply", "content" => "non-empty"), r3 = Reply.new("title" => "Yet another reply"), r4 = Reply.new("title" => "The last reply", "content" => "non-empty")]
-    assert !t.valid?
-    assert t.errors[:replies].any?
+    assert_not_predicate t, :valid?
+    assert_predicate t.errors[:replies], :any?
     assert_equal 1, r.errors.count  # make sure all associated objects have been validated
     assert_equal 0, r2.errors.count
     assert_equal 1, r3.errors.count
     assert_equal 0, r4.errors.count
     r.content = r3.content = "non-empty"
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_associated_one
@@ -31,10 +31,10 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Topic.validates_presence_of(:content)
     r = Reply.new("title" => "A reply", "content" => "with content!")
     r.topic = Topic.create("title" => "uhohuhoh")
-    assert !r.valid?
-    assert r.errors[:topic].any?
+    assert_not_predicate r, :valid?
+    assert_predicate r.errors[:topic], :any?
     r.topic.content = "non-empty"
-    assert r.valid?
+    assert_predicate r, :valid?
   end
 
   def test_validates_associated_marked_for_destruction
@@ -42,9 +42,9 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Reply.validates_presence_of(:content)
     t = Topic.new
     t.replies << Reply.new
-    assert t.invalid?
+    assert_predicate t, :invalid?
     t.replies.first.mark_for_destruction
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_associated_without_marked_for_destruction
@@ -56,7 +56,7 @@ class AssociationValidationTest < ActiveRecord::TestCase
     Topic.validates_associated(:replies)
     t = Topic.new
     t.define_singleton_method(:replies) { [reply.new] }
-    assert t.valid?
+    assert_predicate t, :valid?
   end
 
   def test_validates_associated_with_custom_message_using_quotes
@@ -71,11 +71,11 @@ class AssociationValidationTest < ActiveRecord::TestCase
   def test_validates_associated_missing
     Reply.validates_presence_of(:topic)
     r = Reply.create("title" => "A reply", "content" => "with content!")
-    assert !r.valid?
-    assert r.errors[:topic].any?
+    assert_not_predicate r, :valid?
+    assert_predicate r.errors[:topic], :any?
 
     r.topic = Topic.first
-    assert r.valid?
+    assert_predicate r, :valid?
   end
 
   def test_validates_presence_of_belongs_to_association__parent_is_new_record
diff --git a/activerecord/test/cases/validations/length_validation_test.rb b/activerecord/test/cases/validations/length_validation_test.rb
index 87ce4c6f37..62cd89041a 100644
--- a/activerecord/test/cases/validations/length_validation_test.rb
+++ b/activerecord/test/cases/validations/length_validation_test.rb
@@ -18,47 +18,47 @@ class LengthValidationTest < ActiveRecord::TestCase
     assert_nothing_raised { @owner.validates_size_of :pets, minimum: 1 }
     o = @owner.new("name" => "nopets")
     assert !o.save
-    assert o.errors[:pets].any?
+    assert_predicate o.errors[:pets], :any?
     o.pets.build("name" => "apet")
-    assert o.valid?
+    assert_predicate o, :valid?
   end
 
   def test_validates_size_of_association_using_within
     assert_nothing_raised { @owner.validates_size_of :pets, within: 1..2 }
     o = @owner.new("name" => "nopets")
     assert !o.save
-    assert o.errors[:pets].any?
+    assert_predicate o.errors[:pets], :any?
 
     o.pets.build("name" => "apet")
-    assert o.valid?
+    assert_predicate o, :valid?
 
     2.times { o.pets.build("name" => "apet") }
     assert !o.save
-    assert o.errors[:pets].any?
+    assert_predicate o.errors[:pets], :any?
   end
 
   def test_validates_size_of_association_utf8
     @owner.validates_size_of :pets, minimum: 1
     o = @owner.new("name" => "あいうえおかきくけこ")
     assert !o.save
-    assert o.errors[:pets].any?
+    assert_predicate o.errors[:pets], :any?
     o.pets.build("name" => "あいうえおかきくけこ")
-    assert o.valid?
+    assert_predicate o, :valid?
   end
 
   def test_validates_size_of_respects_records_marked_for_destruction
     @owner.validates_size_of :pets, minimum: 1
     owner = @owner.new
     assert_not owner.save
-    assert owner.errors[:pets].any?
+    assert_predicate owner.errors[:pets], :any?
     pet = owner.pets.build
-    assert owner.valid?
+    assert_predicate owner, :valid?
     assert owner.save
 
     pet_count = Pet.count
-    assert_not owner.update_attributes pets_attributes: [ { _destroy: 1, id: pet.id } ]
-    assert_not owner.valid?
-    assert owner.errors[:pets].any?
+    assert_not owner.update pets_attributes: [ { _destroy: 1, id: pet.id } ]
+    assert_not_predicate owner, :valid?
+    assert_predicate owner.errors[:pets], :any?
     assert_equal pet_count, Pet.count
   end
 
@@ -70,11 +70,11 @@ class LengthValidationTest < ActiveRecord::TestCase
 
       pet = Pet.create!(name: "Fancy Pants", nickname: "Fancy")
 
-      assert pet.valid?
+      assert_predicate pet, :valid?
 
       pet.nickname = ""
 
-      assert pet.invalid?
+      assert_predicate pet, :invalid?
     end
   end
 end
diff --git a/activerecord/test/cases/validations/presence_validation_test.rb b/activerecord/test/cases/validations/presence_validation_test.rb
index 3ab1567b51..63c3f67da2 100644
--- a/activerecord/test/cases/validations/presence_validation_test.rb
+++ b/activerecord/test/cases/validations/presence_validation_test.rb
@@ -15,10 +15,10 @@ class PresenceValidationTest < ActiveRecord::TestCase
   def test_validates_presence_of_non_association
     Boy.validates_presence_of(:name)
     b = Boy.new
-    assert b.invalid?
+    assert_predicate b, :invalid?
 
     b.name = "Alex"
-    assert b.valid?
+    assert_predicate b, :valid?
   end
 
   def test_validates_presence_of_has_one
@@ -33,23 +33,23 @@ class PresenceValidationTest < ActiveRecord::TestCase
     b = Boy.new
     f = Face.new
     b.face = f
-    assert b.valid?
+    assert_predicate b, :valid?
 
     f.mark_for_destruction
-    assert b.invalid?
+    assert_predicate b, :invalid?
   end
 
   def test_validates_presence_of_has_many_marked_for_destruction
     Boy.validates_presence_of(:interests)
     b = Boy.new
     b.interests << [i1 = Interest.new, i2 = Interest.new]
-    assert b.valid?
+    assert_predicate b, :valid?
 
     i1.mark_for_destruction
-    assert b.valid?
+    assert_predicate b, :valid?
 
     i2.mark_for_destruction
-    assert b.invalid?
+    assert_predicate b, :invalid?
   end
 
   def test_validates_presence_doesnt_convert_to_array
@@ -74,11 +74,11 @@ class PresenceValidationTest < ActiveRecord::TestCase
       Interest.validates_presence_of(:abbreviation)
 
       interest = Interest.create!(topic: "Thought Leadering", abbreviation: "tl")
-      assert interest.valid?
+      assert_predicate interest, :valid?
 
       interest.abbreviation = ""
 
-      assert interest.invalid?
+      assert_predicate interest, :invalid?
     end
   end
 
diff --git a/activerecord/test/cases/validations/uniqueness_validation_test.rb b/activerecord/test/cases/validations/uniqueness_validation_test.rb
index a10567f066..941aed5402 100644
--- a/activerecord/test/cases/validations/uniqueness_validation_test.rb
+++ b/activerecord/test/cases/validations/uniqueness_validation_test.rb
@@ -62,7 +62,7 @@ class TopicWithAfterCreate < Topic
   after_create :set_author
 
   def set_author
-    update_attributes!(author_name: "#{title} #{id}")
+    update!(author_name: "#{title} #{id}")
   end
 end
 
@@ -96,7 +96,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.validates_uniqueness_of(:new_title)
 
     topic = Topic.new(new_title: "abc")
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_validates_uniqueness_with_nil_value
@@ -116,7 +116,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.create!("title" => "abc")
 
     t2 = Topic.new("title" => "abc")
-    assert !t2.valid?
+    assert_not_predicate t2, :valid?
     assert t2.errors[:title]
   end
 
@@ -259,15 +259,15 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     t2 = Topic.new("title" => "I'm UNIQUE!", :parent_id => 1)
     assert !t2.valid?, "Shouldn't be valid"
     assert !t2.save, "Shouldn't save t2 as unique"
-    assert t2.errors[:title].any?
-    assert t2.errors[:parent_id].any?
+    assert_predicate t2.errors[:title], :any?
+    assert_predicate t2.errors[:parent_id], :any?
     assert_equal ["has already been taken"], t2.errors[:title]
 
     t2.title = "I'm truly UNIQUE!"
     assert !t2.valid?, "Shouldn't be valid"
     assert !t2.save, "Shouldn't save t2 as unique"
-    assert t2.errors[:title].empty?
-    assert t2.errors[:parent_id].any?
+    assert_empty t2.errors[:title]
+    assert_predicate t2.errors[:parent_id], :any?
 
     t2.parent_id = 4
     assert t2.save, "Should now save t2 as unique"
@@ -326,15 +326,15 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     t2 = Topic.new("title" => "I'M UNIQUE!")
     assert t2.valid?, "Should be valid"
     assert t2.save, "Should save t2 as unique"
-    assert t2.errors[:title].empty?
-    assert t2.errors[:parent_id].empty?
+    assert_empty t2.errors[:title]
+    assert_empty t2.errors[:parent_id]
     assert_not_equal ["has already been taken"], t2.errors[:title]
 
     t3 = Topic.new("title" => "I'M uNiQUe!")
     assert t3.valid?, "Should be valid"
     assert t3.save, "Should save t2 as unique"
-    assert t3.errors[:title].empty?
-    assert t3.errors[:parent_id].empty?
+    assert_empty t3.errors[:title]
+    assert_empty t3.errors[:parent_id]
     assert_not_equal ["has already been taken"], t3.errors[:title]
   end
 
@@ -343,7 +343,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     Topic.create!("title" => 101)
 
     t2 = Topic.new("title" => 101)
-    assert !t2.valid?
+    assert_not_predicate t2, :valid?
     assert t2.errors[:title]
   end
 
@@ -360,7 +360,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
       t1 = Topic.new("title" => "I'm unique!", "author_name" => "Mary")
       assert t1.save
       t2 = Topic.new("title" => "I'm unique!", "author_name" => "David")
-      assert !t2.valid?
+      assert_not_predicate t2, :valid?
     end
   end
 
@@ -460,16 +460,16 @@ class UniquenessValidationTest < ActiveRecord::TestCase
 
   def test_validate_uniqueness_on_existing_relation
     event = Event.create
-    assert TopicWithUniqEvent.create(event: event).valid?
+    assert_predicate TopicWithUniqEvent.create(event: event), :valid?
 
     topic = TopicWithUniqEvent.new(event: event)
-    assert_not topic.valid?
+    assert_not_predicate topic, :valid?
     assert_equal ["has already been taken"], topic.errors[:event]
   end
 
   def test_validate_uniqueness_on_empty_relation
     topic = TopicWithUniqEvent.new
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_validate_uniqueness_of_custom_primary_key
@@ -488,7 +488,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     key2 = klass.create!(key_number: 11)
 
     key2.key_number = 10
-    assert_not key2.valid?
+    assert_not_predicate key2, :valid?
   end
 
   def test_validate_uniqueness_without_primary_key
@@ -501,8 +501,8 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     end
 
     abc = klass.create!(dashboard_id: "abc")
-    assert klass.new(dashboard_id: "xyz").valid?
-    assert_not klass.new(dashboard_id: "abc").valid?
+    assert_predicate klass.new(dashboard_id: "xyz"), :valid?
+    assert_not_predicate klass.new(dashboard_id: "abc"), :valid?
 
     abc.dashboard_id = "def"
 
@@ -530,7 +530,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert topic.author_name.start_with?("Title1")
 
     topic2 = TopicWithAfterCreate.new(title: "Title1")
-    refute topic2.valid?
+    assert_not_predicate topic2, :valid?
     assert_equal(["has already been taken"], topic2.errors[:title])
   end
 
@@ -550,7 +550,7 @@ class UniquenessValidationTest < ActiveRecord::TestCase
     assert_empty item.errors
 
     item2 = CoolTopic.new(id: item.id, title: "MyItem2")
-    refute item2.valid?
+    assert_not_predicate item2, :valid?
 
     assert_equal(["has already been taken"], item2.errors[:id])
   end
diff --git a/activerecord/test/cases/validations_test.rb b/activerecord/test/cases/validations_test.rb
index 14623c43d2..6c83bbd15c 100644
--- a/activerecord/test/cases/validations_test.rb
+++ b/activerecord/test/cases/validations_test.rb
@@ -19,7 +19,7 @@ class ValidationsTest < ActiveRecord::TestCase
   def test_valid_uses_create_context_when_new
     r = WrongReply.new
     r.title = "Wrong Create"
-    assert_not r.valid?
+    assert_not_predicate r, :valid?
     assert r.errors[:title].any?, "A reply with a bad title should mark that attribute as invalid"
     assert_equal ["is Wrong Create"], r.errors[:title], "A reply with a bad content should contain an error"
   end
@@ -139,7 +139,7 @@ class ValidationsTest < ActiveRecord::TestCase
 
   def test_throw_away_typing
     d = Developer.new("name" => "David", "salary" => "100,000")
-    assert !d.valid?
+    assert_not_predicate d, :valid?
     assert_equal 100, d.salary
     assert_equal "100,000", d.salary_before_type_cast
   end
@@ -166,7 +166,7 @@ class ValidationsTest < ActiveRecord::TestCase
     topic = klass.new(wibble: "123-4567")
     topic.wibble.gsub!("-", "")
 
-    assert topic.valid?
+    assert_predicate topic, :valid?
   end
 
   def test_numericality_validation_checks_against_raw_value
@@ -178,9 +178,9 @@ class ValidationsTest < ActiveRecord::TestCase
       validates_numericality_of :wibble, greater_than_or_equal_to: BigDecimal("97.18")
     end
 
-    assert_not klass.new(wibble: "97.179").valid?
-    assert_not klass.new(wibble: 97.179).valid?
-    assert_not klass.new(wibble: BigDecimal("97.179")).valid?
+    assert_not_predicate klass.new(wibble: "97.179"), :valid?
+    assert_not_predicate klass.new(wibble: 97.179), :valid?
+    assert_not_predicate klass.new(wibble: BigDecimal("97.179")), :valid?
   end
 
   def test_acceptance_validator_doesnt_require_db_connection
diff --git a/activerecord/test/cases/yaml_serialization_test.rb b/activerecord/test/cases/yaml_serialization_test.rb
index 578881f754..60ebdce178 100644
--- a/activerecord/test/cases/yaml_serialization_test.rb
+++ b/activerecord/test/cases/yaml_serialization_test.rb
@@ -96,7 +96,7 @@ class YamlSerializationTest < ActiveRecord::TestCase
   def test_deserializing_rails_41_yaml
     topic = YAML.load(yaml_fixture("rails_4_1"))
 
-    assert topic.new_record?
+    assert_predicate topic, :new_record?
     assert_nil topic.id
     assert_equal "The First Topic", topic.title
     assert_equal({ omg: :lol }, topic.content)
@@ -105,7 +105,7 @@ class YamlSerializationTest < ActiveRecord::TestCase
   def test_deserializing_rails_4_2_0_yaml
     topic = YAML.load(yaml_fixture("rails_4_2_0"))
 
-    assert_not topic.new_record?
+    assert_not_predicate topic, :new_record?
     assert_equal 1, topic.id
     assert_equal "The First Topic", topic.title
     assert_equal("Have a nice day", topic.content)
diff --git a/activerecord/test/fixtures/.gitignore b/activerecord/test/fixtures/.gitignore
deleted file mode 100644
index 885029a512..0000000000
--- a/activerecord/test/fixtures/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-*.sqlite*
\ No newline at end of file
diff --git a/activerecord/test/fixtures/customers.yml b/activerecord/test/fixtures/customers.yml
index 0399ff83b9..7d6c1366d0 100644
--- a/activerecord/test/fixtures/customers.yml
+++ b/activerecord/test/fixtures/customers.yml
@@ -23,4 +23,13 @@ barney:
   address_street: Quiet Road
   address_city: Peaceful Town
   address_country: Tranquil Land
-  gps_location: NULL
\ No newline at end of file
+  gps_location: NULL
+
+mary:
+  id: 4
+  name: Mary
+  balance: 1
+  address_street: Funny Street
+  address_city: Peaceful Town
+  address_country: Nation Land
+  gps_location: NULL
diff --git a/activerecord/test/fixtures/minimalistics.yml b/activerecord/test/fixtures/minimalistics.yml
index c3ec546209..83df0551bc 100644
--- a/activerecord/test/fixtures/minimalistics.yml
+++ b/activerecord/test/fixtures/minimalistics.yml
@@ -1,2 +1,5 @@
+zero:
+  id: 0
+
 first:
   id: 1
diff --git a/activerecord/test/fixtures/teapots.yml b/activerecord/test/fixtures/teapots.yml
deleted file mode 100644
index ff515beb45..0000000000
--- a/activerecord/test/fixtures/teapots.yml
+++ /dev/null
@@ -1,3 +0,0 @@
-bob:
-  id: 1
-  name: Bob
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 27da886e1c..bd12cdf7ef 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -8,6 +8,7 @@ class Author < ActiveRecord::Base
   has_many :posts_with_comments, -> { includes(:comments) }, class_name: "Post"
   has_many :popular_grouped_posts, -> { includes(:comments).group("type").having("SUM(comments_count) > 1").select("type") }, class_name: "Post"
   has_many :posts_with_comments_sorted_by_comment_id, -> { includes(:comments).order("comments.id") }, class_name: "Post"
+  has_many :posts_sorted_by_id, -> { order(:id) }, class_name: "Post"
   has_many :posts_sorted_by_id_limited, -> { order("posts.id").limit(1) }, class_name: "Post"
   has_many :posts_with_categories, -> { includes(:categories) }, class_name: "Post"
   has_many :posts_with_comments_and_categories, -> { includes(:comments, :categories).order("posts.id") }, class_name: "Post"
@@ -40,7 +41,7 @@ class Author < ActiveRecord::Base
            -> { where(title: "Welcome to the weblog").where(Post.arel_table[:comments_count].gt(0)) },
            class_name: "Post"
 
-  has_many :comments_desc, -> { order("comments.id DESC") }, through: :posts, source: :comments
+  has_many :comments_desc, -> { order("comments.id DESC") }, through: :posts_sorted_by_id, source: :comments
   has_many :unordered_comments, -> { unscope(:order).distinct }, through: :posts_sorted_by_id_limited, source: :comments
   has_many :funky_comments, through: :posts, source: :comments
   has_many :ordered_uniq_comments, -> { distinct.order("comments.id") }, through: :posts, source: :comments
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index 5ab433f2d9..f0f0576709 100644
--- a/activerecord/test/models/comment.rb
+++ b/activerecord/test/models/comment.rb
@@ -76,7 +76,7 @@ class CommentThatAutomaticallyAltersPostBody < Comment
   belongs_to :post, class_name: "PostThatLoadsCommentsInAnAfterSaveHook", foreign_key: :post_id
 
   after_save do |comment|
-    comment.post.update_attributes(body: "Automatically altered")
+    comment.post.update(body: "Automatically altered")
   end
 end
 
@@ -87,6 +87,6 @@ end
 
 class CommentWithAfterCreateUpdate < Comment
   after_create do
-    update_attributes(body: "bar")
+    update(body: "bar")
   end
 end
diff --git a/activerecord/test/models/customer.rb b/activerecord/test/models/customer.rb
index 524a9d7bd9..bc501a5ce0 100644
--- a/activerecord/test/models/customer.rb
+++ b/activerecord/test/models/customer.rb
@@ -4,7 +4,7 @@ class Customer < ActiveRecord::Base
   cattr_accessor :gps_conversion_was_run
 
   composed_of :address, mapping: [ %w(address_street street), %w(address_city city), %w(address_country country) ], allow_nil: true
-  composed_of :balance, class_name: "Money", mapping: %w(balance amount), converter: Proc.new(&:to_money)
+  composed_of :balance, class_name: "Money", mapping: %w(balance amount)
   composed_of :gps_location, allow_nil: true
   composed_of :non_blank_gps_location, class_name: "GpsLocation", allow_nil: true, mapping: %w(gps_location gps_location),
               converter: lambda { |gps| self.gps_conversion_was_run = true; gps.blank? ? nil : GpsLocation.new(gps) }
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 780a2c17f5..54eb5e6783 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -106,6 +106,9 @@ class Post < ActiveRecord::Base
     end
   end
 
+  has_many :indestructible_taggings, as: :taggable, counter_cache: :indestructible_tags_count
+  has_many :indestructible_tags, through: :indestructible_taggings, source: :tag
+
   has_many :taggings_with_delete_all, class_name: "Tagging", as: :taggable, dependent: :delete_all, counter_cache: :taggings_with_delete_all_count
   has_many :taggings_with_destroy, class_name: "Tagging", as: :taggable, dependent: :destroy, counter_cache: :taggings_with_destroy_count
 
@@ -323,5 +326,13 @@ class FakeKlass
     def enforce_raw_sql_whitelist(*args)
       # noop
     end
+
+    def arel_table
+      Post.arel_table
+    end
+
+    def predicate_builder
+      Post.predicate_builder
+    end
   end
 end
diff --git a/activerecord/test/models/tagging.rb b/activerecord/test/models/tagging.rb
index 861fde633f..6d4230f6f4 100644
--- a/activerecord/test/models/tagging.rb
+++ b/activerecord/test/models/tagging.rb
@@ -14,3 +14,7 @@ class Tagging < ActiveRecord::Base
   belongs_to :taggable, polymorphic: true, counter_cache: :tags_count
   has_many :things, through: :taggable
 end
+
+class IndestructibleTagging < Tagging
+  before_destroy { throw :abort }
+end
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 3205c4c20a..7d008eecd5 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -690,6 +690,7 @@ ActiveRecord::Schema.define do
     t.integer :taggings_with_delete_all_count, default: 0
     t.integer :taggings_with_destroy_count, default: 0
     t.integer :tags_count, default: 0
+    t.integer :indestructible_tags_count, default: 0
     t.integer :tags_with_destroy_count, default: 0
     t.integer :tags_with_nullify_count, default: 0
   end
@@ -847,6 +848,7 @@ ActiveRecord::Schema.define do
     t.column :taggable_type, :string
     t.column :taggable_id, :integer
     t.string :comment
+    t.string :type
   end
 
   create_table :tasks, force: true do |t|
diff --git a/activestorage/.gitignore b/activestorage/.gitignore
index a532335bdd..3e78878ffc 100644
--- a/activestorage/.gitignore
+++ b/activestorage/.gitignore
@@ -1,6 +1,6 @@
-.byebug_history
-node_modules
-test/dummy/db/*.sqlite3
-test/dummy/db/*.sqlite3-journal
-test/dummy/log/*.log
-test/dummy/tmp/
+/src/
+/test/dummy/db/*.sqlite3
+/test/dummy/db/*.sqlite3-journal
+/test/dummy/log/*.log
+/test/dummy/tmp/
+/test/service/configurations.yml
diff --git a/activestorage/CHANGELOG.md b/activestorage/CHANGELOG.md
index 5e01297fc1..cc21c1f75a 100644
--- a/activestorage/CHANGELOG.md
+++ b/activestorage/CHANGELOG.md
@@ -1,26 +1,15 @@
-*   Use `after_destroy_commit` instead of `before_destroy` for purging
-    attachments when a record is destroyed.
+## Rails 6.0.0.alpha (Unreleased) ##
 
-    *Hiroki Zenigami*
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
+    *Jeremy Daer*
 
-*   Force `:attachment` disposition for specific, configurable content types.
-    This mitigates possible security issues such as XSS or phishing when
-    serving them inline. A list of such content types is included by default,
-    and can be configured via `content_types_to_serve_as_binary`.
+*   Add source code to published npm package
 
-    *Rosa Gutierrez*
+    This allows activestorage users to depend on the javascript source code
+    rather than the compiled code, which can produce smaller javascript bundles.
 
+    *Richard Macklin*
 
-## Rails 5.2.0.beta2 (November 28, 2017) ##
 
-*   Fix the gem adding the migrations files to the package.
-
-    *Yuji Yaginuma*
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Added to Rails.
-
-    *DHH*
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activestorage/CHANGELOG.md) for previous changes.
diff --git a/activestorage/activestorage.gemspec b/activestorage/activestorage.gemspec
index d135324700..df7801a671 100644
--- a/activestorage/activestorage.gemspec
+++ b/activestorage/activestorage.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Local and cloud file storage framework."
   s.description = "Attach cloud and local files in Rails applications."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/activestorage/app/models/active_storage/blob.rb b/activestorage/app/models/active_storage/blob.rb
index 7067c58259..31fbc66965 100644
--- a/activestorage/app/models/active_storage/blob.rb
+++ b/activestorage/app/models/active_storage/blob.rb
@@ -14,17 +14,25 @@
 # update a blob's metadata on a subsequent pass, but you should not update the key or change the uploaded file.
 # If you need to create a derivative or otherwise change the blob, simply create a new blob and purge the old one.
 class ActiveStorage::Blob < ActiveRecord::Base
-  include Analyzable, Identifiable, Representable
+  require_dependency "active_storage/blob/analyzable"
+  require_dependency "active_storage/blob/identifiable"
+  require_dependency "active_storage/blob/representable"
+
+  include Analyzable
+  include Identifiable
+  include Representable
 
   self.table_name = "active_storage_blobs"
 
   has_secure_token :key
-  store :metadata, accessors: [ :analyzed, :identified ], coder: JSON
+  store :metadata, accessors: [ :analyzed, :identified ], coder: ActiveRecord::Coders::JSON
 
   class_attribute :service
 
   has_many :attachments
 
+  scope :unattached, -> { left_joins(:attachments).where(ActiveStorage::Attachment.table_name => { blob_id: nil }) }
+
   class << self
     # You can used the signed ID of a blob to refer to it on the client side without fear of tampering.
     # This is particularly helpful for direct uploads where the client-side needs to refer to the blob
@@ -109,8 +117,11 @@ class ActiveStorage::Blob < ActiveRecord::Base
   # with users. Instead, the +service_url+ should only be exposed as a redirect from a stable, possibly authenticated URL.
   # Hiding the +service_url+ behind a redirect also gives you the power to change services without updating all URLs. And
   # it allows permanent URLs that redirect to the +service_url+ to be cached in the view.
-  def service_url(expires_in: service.url_expires_in, disposition: :inline, filename: self.filename)
-    service.url key, expires_in: expires_in, disposition: forcibly_serve_as_binary? ? :attachment : disposition, filename: filename, content_type: content_type
+  def service_url(expires_in: service.url_expires_in, disposition: :inline, filename: nil, **options)
+    filename = ActiveStorage::Filename.wrap(filename || self.filename)
+
+    service.url key, expires_in: expires_in, filename: filename, content_type: content_type,
+      disposition: forcibly_serve_as_binary? ? :attachment : disposition, **options
   end
 
   # Returns a URL that can be used to directly upload a file for this blob on the service. This URL is intended to be
diff --git a/activestorage/app/models/active_storage/blob/identifiable.rb b/activestorage/app/models/active_storage/blob/identifiable.rb
index 40ca84ac70..dbe03cfa6c 100644
--- a/activestorage/app/models/active_storage/blob/identifiable.rb
+++ b/activestorage/app/models/active_storage/blob/identifiable.rb
@@ -2,10 +2,15 @@
 
 module ActiveStorage::Blob::Identifiable
   def identify
-    ActiveStorage::Identification.new(self).apply
+    update!(content_type: identification.content_type, identified: true) unless identified?
   end
 
   def identified?
     identified
   end
+
+  private
+    def identification
+      ActiveStorage::Identification.new self
+    end
 end
diff --git a/activestorage/app/models/active_storage/filename.rb b/activestorage/app/models/active_storage/filename.rb
index b9413dec95..bebb5e61b3 100644
--- a/activestorage/app/models/active_storage/filename.rb
+++ b/activestorage/app/models/active_storage/filename.rb
@@ -3,8 +3,18 @@
 # Encapsulates a string representing a filename to provide convenient access to parts of it and sanitization.
 # A Filename instance is returned by ActiveStorage::Blob#filename, and is comparable so it can be used for sorting.
 class ActiveStorage::Filename
+  require_dependency "active_storage/filename/parameters"
+
   include Comparable
 
+  class << self
+    # Returns a Filename instance based on the given filename. If the filename is a Filename, it is
+    # returned unmodified. If it is a String, it is passed to ActiveStorage::Filename.new.
+    def wrap(filename)
+      filename.kind_of?(self) ? filename : new(filename)
+    end
+  end
+
   def initialize(filename)
     @filename = filename
   end
diff --git a/activestorage/app/models/active_storage/identification.rb b/activestorage/app/models/active_storage/identification.rb
index 4f295257ae..8d334ae1ea 100644
--- a/activestorage/app/models/active_storage/identification.rb
+++ b/activestorage/app/models/active_storage/identification.rb
@@ -1,25 +1,22 @@
 # frozen_string_literal: true
 
-class ActiveStorage::Identification
+require "net/http"
+
+class ActiveStorage::Identification #:nodoc:
   attr_reader :blob
 
   def initialize(blob)
     @blob = blob
   end
 
-  def apply
-    blob.update!(content_type: content_type, identified: true) unless blob.identified?
+  def content_type
+    Marcel::MimeType.for(identifiable_chunk, name: filename, declared_type: declared_content_type)
   end
 
   private
-    def content_type
-      Marcel::MimeType.for(identifiable_chunk, name: filename, declared_type: declared_content_type)
-    end
-
-
     def identifiable_chunk
       Net::HTTP.start(uri.host, uri.port, use_ssl: uri.scheme == "https") do |client|
-        client.get(uri, "Range" => "0-4096").body
+        client.get(uri, "Range" => "bytes=0-4095").body
       end
     end
 
diff --git a/activestorage/app/models/active_storage/preview.rb b/activestorage/app/models/active_storage/preview.rb
index be5053edae..45efd26214 100644
--- a/activestorage/app/models/active_storage/preview.rb
+++ b/activestorage/app/models/active_storage/preview.rb
@@ -24,7 +24,7 @@
 # The built-in previewers rely on third-party system libraries:
 #
 # * {ffmpeg}[https://www.ffmpeg.org]
-# * {mupdf}[https://mupdf.com]
+# * {mupdf}[https://mupdf.com] (version 1.8 or newer)
 #
 # These libraries are not provided by Rails. You must install them yourself to use the built-in previewers. Before you
 # install and use third-party software, make sure you understand the licensing implications of doing so.
diff --git a/activestorage/app/models/active_storage/variant.rb b/activestorage/app/models/active_storage/variant.rb
index e08a2271ec..a95a4bfd7c 100644
--- a/activestorage/app/models/active_storage/variant.rb
+++ b/activestorage/app/models/active_storage/variant.rb
@@ -115,7 +115,7 @@ class ActiveStorage::Variant
 
     def download_image
       require "mini_magick"
-      MiniMagick::Image.create { |file| download_blob_to(file) }
+      MiniMagick::Image.create(blob.filename.extension_with_delimiter) { |file| download_blob_to(file) }
     end
 
     def transform(image)
diff --git a/activestorage/app/models/active_storage/variation.rb b/activestorage/app/models/active_storage/variation.rb
index da4af62666..12e7f9f0b5 100644
--- a/activestorage/app/models/active_storage/variation.rb
+++ b/activestorage/app/models/active_storage/variation.rb
@@ -8,6 +8,14 @@
 #
 #   ActiveStorage::Variation.new(resize: "100x100", monochrome: true, trim: true, rotate: "-90")
 #
+# You can also combine multiple transformations in one step, e.g. for center-weighted cropping:
+#
+#   ActiveStorage::Variation.new(combine_options: {
+#     resize: "100x100^",
+#     gravity: "center",
+#     crop: "100x100+0+0",
+#   })
+#
 # A list of all possible transformations is available at https://www.imagemagick.org/script/mogrify.php.
 class ActiveStorage::Variation
   attr_reader :transformations
diff --git a/activestorage/lib/active_storage/analyzer/image_analyzer.rb b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
index 5231168a7c..3b39de91be 100644
--- a/activestorage/lib/active_storage/analyzer/image_analyzer.rb
+++ b/activestorage/lib/active_storage/analyzer/image_analyzer.rb
@@ -3,6 +3,8 @@
 module ActiveStorage
   # Extracts width and height in pixels from an image blob.
   #
+  # If the image contains EXIF data indicating its angle is 90 or 270 degrees, its width and height are swapped for convenience.
+  #
   # Example:
   #
   #   ActiveStorage::Analyzer::ImageAnalyzer.new(blob).metadata
@@ -17,7 +19,11 @@ module ActiveStorage
 
     def metadata
       read_image do |image|
-        { width: image.width, height: image.height }
+        if rotated_image?(image)
+          { width: image.height, height: image.width }
+        else
+          { width: image.width, height: image.height }
+        end
       end
     rescue LoadError
       logger.info "Skipping image analysis because the mini_magick gem isn't installed"
@@ -31,5 +37,9 @@ module ActiveStorage
           yield MiniMagick::Image.new(file.path)
         end
       end
+
+      def rotated_image?(image)
+        %w[ RightTop LeftBottom ].include?(image["%[orientation]"])
+      end
   end
 end
diff --git a/activestorage/lib/active_storage/analyzer/video_analyzer.rb b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
index aa532da201..656e362187 100644
--- a/activestorage/lib/active_storage/analyzer/video_analyzer.rb
+++ b/activestorage/lib/active_storage/analyzer/video_analyzer.rb
@@ -9,12 +9,12 @@ module ActiveStorage
   # * Height (pixels)
   # * Duration (seconds)
   # * Angle (degrees)
-  # * Aspect ratio
+  # * Display aspect ratio
   #
   # Example:
   #
   #   ActiveStorage::VideoAnalyzer.new(blob).metadata
-  #   # => { width: 640, height: 480, duration: 5.0, angle: 0, aspect_ratio: [4, 3] }
+  #   # => { width: 640.0, height: 480.0, duration: 5.0, angle: 0, display_aspect_ratio: [4, 3] }
   #
   # When a video's angle is 90 or 270 degrees, its width and height are automatically swapped for convenience.
   #
@@ -25,24 +25,24 @@ module ActiveStorage
     end
 
     def metadata
-      { width: width, height: height, duration: duration, angle: angle, aspect_ratio: aspect_ratio }.compact
+      { width: width, height: height, duration: duration, angle: angle, display_aspect_ratio: display_aspect_ratio }.compact
     end
 
     private
       def width
-        rotated? ? raw_height : raw_width
+        if rotated?
+          computed_height || encoded_height
+        else
+          encoded_width
+        end
       end
 
       def height
-        rotated? ? raw_width : raw_height
-      end
-
-      def raw_width
-        Integer(video_stream["width"]) if video_stream["width"]
-      end
-
-      def raw_height
-        Integer(video_stream["height"]) if video_stream["height"]
+        if rotated?
+          encoded_width
+        else
+          computed_height || encoded_height
+        end
       end
 
       def duration
@@ -53,16 +53,40 @@ module ActiveStorage
         Integer(tags["rotate"]) if tags["rotate"]
       end
 
-      def aspect_ratio
+      def display_aspect_ratio
         if descriptor = video_stream["display_aspect_ratio"]
-          descriptor.split(":", 2).collect(&:to_i)
+          if terms = descriptor.split(":", 2)
+            numerator   = Integer(terms[0])
+            denominator = Integer(terms[1])
+
+            [numerator, denominator] unless numerator == 0
+          end
         end
       end
 
+
       def rotated?
         angle == 90 || angle == 270
       end
 
+      def computed_height
+        if encoded_width && display_height_scale
+          encoded_width * display_height_scale
+        end
+      end
+
+      def encoded_width
+        @encoded_width ||= Float(video_stream["width"]) if video_stream["width"]
+      end
+
+      def encoded_height
+        @encoded_height ||= Float(video_stream["height"]) if video_stream["height"]
+      end
+
+      def display_height_scale
+        @display_height_scale ||= Float(display_aspect_ratio.last) / display_aspect_ratio.first if display_aspect_ratio
+      end
+
 
       def tags
         @tags ||= video_stream["tags"] || {}
diff --git a/activestorage/lib/active_storage/downloading.rb b/activestorage/lib/active_storage/downloading.rb
index a57fda49b4..f2a1fffdcb 100644
--- a/activestorage/lib/active_storage/downloading.rb
+++ b/activestorage/lib/active_storage/downloading.rb
@@ -1,25 +1,37 @@
 # frozen_string_literal: true
 
+require "tmpdir"
+
 module ActiveStorage
   module Downloading
     private
       # Opens a new tempfile in #tempdir and copies blob data into it. Yields the tempfile.
-      def download_blob_to_tempfile # :doc:
-        Tempfile.open([ "ActiveStorage", blob.filename.extension_with_delimiter ], tempdir) do |file|
+      def download_blob_to_tempfile #:doc:
+        open_tempfile_for_blob do |file|
           download_blob_to file
           yield file
         end
       end
 
+      def open_tempfile_for_blob
+        tempfile = Tempfile.open([ "ActiveStorage", blob.filename.extension_with_delimiter ], tempdir)
+
+        begin
+          yield tempfile
+        ensure
+          tempfile.close!
+        end
+      end
+
       # Efficiently downloads blob data into the given file.
-      def download_blob_to(file) # :doc:
+      def download_blob_to(file) #:doc:
         file.binmode
         blob.download { |chunk| file.write(chunk) }
         file.rewind
       end
 
       # Returns the directory in which tempfiles should be opened. Defaults to +Dir.tmpdir+.
-      def tempdir # :doc:
+      def tempdir #:doc:
         Dir.tmpdir
       end
   end
diff --git a/activestorage/lib/active_storage/engine.rb b/activestorage/lib/active_storage/engine.rb
index 8ba32490b1..9430dde028 100644
--- a/activestorage/lib/active_storage/engine.rb
+++ b/activestorage/lib/active_storage/engine.rb
@@ -18,7 +18,15 @@ module ActiveStorage
     config.active_storage.analyzers = [ ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer ]
     config.active_storage.paths = ActiveSupport::OrderedOptions.new
 
-    config.active_storage.variable_content_types = %w( image/png image/gif image/jpg image/jpeg image/vnd.adobe.photoshop )
+    config.active_storage.variable_content_types = %w(
+      image/png
+      image/gif
+      image/jpg
+      image/jpeg
+      image/vnd.adobe.photoshop
+      image/vnd.microsoft.icon
+    )
+
     config.active_storage.content_types_to_serve_as_binary = %w(
       text/html
       text/javascript
diff --git a/activestorage/lib/active_storage/gem_version.rb b/activestorage/lib/active_storage/gem_version.rb
index f048bb0b77..492620731b 100644
--- a/activestorage/lib/active_storage/gem_version.rb
+++ b/activestorage/lib/active_storage/gem_version.rb
@@ -7,10 +7,10 @@ module ActiveStorage
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activestorage/lib/active_storage/previewer.rb b/activestorage/lib/active_storage/previewer.rb
index dacab1e7df..cf19987d72 100644
--- a/activestorage/lib/active_storage/previewer.rb
+++ b/activestorage/lib/active_storage/previewer.rb
@@ -44,13 +44,23 @@ module ActiveStorage
       # The output tempfile is opened in the directory returned by ActiveStorage::Downloading#tempdir.
       def draw(*argv) #:doc:
         ActiveSupport::Notifications.instrument("preview.active_storage") do
-          Tempfile.open("ActiveStorage", tempdir) do |file|
+          open_tempfile_for_drawing do |file|
             capture(*argv, to: file)
             yield file
           end
         end
       end
 
+      def open_tempfile_for_drawing
+        tempfile = Tempfile.open("ActiveStorage", tempdir)
+
+        begin
+          yield tempfile
+        ensure
+          tempfile.close!
+        end
+      end
+
       def capture(*argv, to:)
         to.binmode
         IO.popen(argv, err: File::NULL) { |out| IO.copy_stream(out, to) }
diff --git a/activestorage/lib/active_storage/service/disk_service.rb b/activestorage/lib/active_storage/service/disk_service.rb
index 27769db584..d17eea9046 100644
--- a/activestorage/lib/active_storage/service/disk_service.rb
+++ b/activestorage/lib/active_storage/service/disk_service.rb
@@ -11,7 +11,7 @@ module ActiveStorage
   class Service::DiskService < Service
     attr_reader :root, :host
 
-    def initialize(root:, host:)
+    def initialize(root:, host: "http://localhost:3000")
       @root, @host = root, host
     end
 
diff --git a/activestorage/package.json b/activestorage/package.json
index 621706000b..d23f8b179e 100644
--- a/activestorage/package.json
+++ b/activestorage/package.json
@@ -1,10 +1,11 @@
 {
   "name": "activestorage",
-  "version": "5.2.0-beta2",
+  "version": "6.0.0-alpha",
   "description": "Attach cloud and local files in Rails applications",
   "main": "app/assets/javascripts/activestorage.js",
   "files": [
-    "app/assets/javascripts/*.js"
+    "app/assets/javascripts/*.js",
+    "src/*.js"
   ],
   "homepage": "http://rubyonrails.org/",
   "repository": {
@@ -16,18 +17,21 @@
   },
   "author": "Javan Makhmali <javan@javan.us>",
   "license": "MIT",
+  "dependencies": {
+    "spark-md5": "^3.0.0"
+  },
   "devDependencies": {
     "babel-core": "^6.25.0",
     "babel-loader": "^7.1.1",
     "babel-preset-env": "^1.6.0",
     "eslint": "^4.3.0",
     "eslint-plugin-import": "^2.7.0",
-    "spark-md5": "^3.0.0",
     "webpack": "^3.4.0"
   },
   "scripts": {
     "prebuild": "yarn lint",
     "build": "webpack -p",
-    "lint": "eslint app/javascript"
+    "lint": "eslint app/javascript",
+    "prepublishOnly": "rm -rf src && cp -R app/javascript/activestorage src"
   }
 }
diff --git a/activestorage/test/analyzer/image_analyzer_test.rb b/activestorage/test/analyzer/image_analyzer_test.rb
index 0d9f24c5c1..f8a38f001a 100644
--- a/activestorage/test/analyzer/image_analyzer_test.rb
+++ b/activestorage/test/analyzer/image_analyzer_test.rb
@@ -8,17 +8,30 @@ require "active_storage/analyzer/image_analyzer"
 class ActiveStorage::Analyzer::ImageAnalyzerTest < ActiveSupport::TestCase
   test "analyzing a JPEG image" do
     blob = create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg")
-    metadata = blob.tap(&:analyze).metadata
+    metadata = extract_metadata_from(blob)
 
     assert_equal 4104, metadata[:width]
     assert_equal 2736, metadata[:height]
   end
 
+  test "analyzing a rotated JPEG image" do
+    blob = create_file_blob(filename: "racecar_rotated.jpg", content_type: "image/jpeg")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 2736, metadata[:width]
+    assert_equal 4104, metadata[:height]
+  end
+
   test "analyzing an SVG image without an XML declaration" do
     blob = create_file_blob(filename: "icon.svg", content_type: "image/svg+xml")
-    metadata = blob.tap(&:analyze).metadata
+    metadata = extract_metadata_from(blob)
 
     assert_equal 792, metadata[:width]
     assert_equal 584, metadata[:height]
   end
+
+  private
+    def extract_metadata_from(blob)
+      blob.tap(&:analyze).metadata
+    end
 end
diff --git a/activestorage/test/analyzer/video_analyzer_test.rb b/activestorage/test/analyzer/video_analyzer_test.rb
index 7fc1cfce06..2612006551 100644
--- a/activestorage/test/analyzer/video_analyzer_test.rb
+++ b/activestorage/test/analyzer/video_analyzer_test.rb
@@ -8,28 +8,52 @@ require "active_storage/analyzer/video_analyzer"
 class ActiveStorage::Analyzer::VideoAnalyzerTest < ActiveSupport::TestCase
   test "analyzing a video" do
     blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
-    metadata = blob.tap(&:analyze).metadata
+    metadata = extract_metadata_from(blob)
 
     assert_equal 640, metadata[:width]
     assert_equal 480, metadata[:height]
-    assert_equal [4, 3], metadata[:aspect_ratio]
+    assert_equal [4, 3], metadata[:display_aspect_ratio]
     assert_equal 5.166648, metadata[:duration]
     assert_not_includes metadata, :angle
   end
 
   test "analyzing a rotated video" do
     blob = create_file_blob(filename: "rotated_video.mp4", content_type: "video/mp4")
-    metadata = blob.tap(&:analyze).metadata
+    metadata = extract_metadata_from(blob)
 
     assert_equal 480, metadata[:width]
     assert_equal 640, metadata[:height]
-    assert_equal [4, 3], metadata[:aspect_ratio]
+    assert_equal [4, 3], metadata[:display_aspect_ratio]
     assert_equal 5.227975, metadata[:duration]
     assert_equal 90, metadata[:angle]
   end
 
+  test "analyzing a video with rectangular samples" do
+    blob = create_file_blob(filename: "video_with_rectangular_samples.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 1280, metadata[:width]
+    assert_equal 720, metadata[:height]
+    assert_equal [16, 9], metadata[:display_aspect_ratio]
+  end
+
+  test "analyzing a video with an undefined display aspect ratio" do
+    blob = create_file_blob(filename: "video_with_undefined_display_aspect_ratio.mp4", content_type: "video/mp4")
+    metadata = extract_metadata_from(blob)
+
+    assert_equal 640, metadata[:width]
+    assert_equal 480, metadata[:height]
+    assert_nil metadata[:display_aspect_ratio]
+  end
+
   test "analyzing a video without a video stream" do
     blob = create_file_blob(filename: "video_without_video_stream.mp4", content_type: "video/mp4")
-    assert_equal({ "analyzed" => true, "identified" => true }, blob.tap(&:analyze).metadata)
+    metadata = extract_metadata_from(blob)
+    assert_equal({ "analyzed" => true, "identified" => true }, metadata)
   end
+
+  private
+    def extract_metadata_from(blob)
+      blob.tap(&:analyze).metadata
+    end
 end
diff --git a/activestorage/test/controllers/direct_uploads_controller_test.rb b/activestorage/test/controllers/direct_uploads_controller_test.rb
index 888767086c..dfffb6bb9c 100644
--- a/activestorage/test/controllers/direct_uploads_controller_test.rb
+++ b/activestorage/test/controllers/direct_uploads_controller_test.rb
@@ -27,7 +27,7 @@ if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].pr
         assert_equal checksum, details["checksum"]
         assert_equal "text/plain", details["content_type"]
         assert_match SERVICE_CONFIGURATIONS[:s3][:bucket], details["direct_upload"]["url"]
-        assert_match(/s3\.(\S+)?amazonaws\.com/, details["direct_upload"]["url"])
+        assert_match(/s3(-[-a-z0-9]+)?\.(\S+)?amazonaws\.com/, details["direct_upload"]["url"])
         assert_equal({ "Content-Type" => "text/plain", "Content-MD5" => checksum }, details["direct_upload"]["headers"])
       end
     end
diff --git a/activestorage/test/controllers/previews_controller_test.rb b/activestorage/test/controllers/previews_controller_test.rb
index 704a466160..b87be6c8b2 100644
--- a/activestorage/test/controllers/previews_controller_test.rb
+++ b/activestorage/test/controllers/previews_controller_test.rb
@@ -14,7 +14,7 @@ class ActiveStorage::PreviewsControllerTest < ActionDispatch::IntegrationTest
       signed_blob_id: @blob.signed_id,
       variation_key: ActiveStorage::Variation.encode(resize: "100x100"))
 
-    assert @blob.preview_image.attached?
+    assert_predicate @blob.preview_image, :attached?
     assert_redirected_to(/report\.png\?.*disposition=inline/)
 
     image = read_image(@blob.preview_image.variant(resize: "100x100"))
diff --git a/activestorage/test/database/setup.rb b/activestorage/test/database/setup.rb
index 705650a25d..daeeb5695b 100644
--- a/activestorage/test/database/setup.rb
+++ b/activestorage/test/database/setup.rb
@@ -3,5 +3,5 @@
 require_relative "create_users_migration"
 
 ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
-ActiveRecord::Migrator.migrate File.expand_path("../../db/migrate", __dir__)
+ActiveRecord::Base.connection.migration_context.migrate
 ActiveStorageCreateUsers.migrate(:up)
diff --git a/activestorage/test/dummy/config/boot.rb b/activestorage/test/dummy/config/boot.rb
index 72516d9255..59459d4ae3 100644
--- a/activestorage/test/dummy/config/boot.rb
+++ b/activestorage/test/dummy/config/boot.rb
@@ -5,7 +5,3 @@ ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../../Gemfile", __dir__)
 
 require "bundler/setup" if File.exist?(ENV["BUNDLE_GEMFILE"])
 $LOAD_PATH.unshift File.expand_path("../../../lib", __dir__)
-
-if %w[s server c console].any? { |a| ARGV.include?(a) }
-  puts "=> Booting Rails"
-end
diff --git a/activestorage/test/dummy/config/storage.yml b/activestorage/test/dummy/config/storage.yml
index 2acc78dc4c..2c6762e0d6 100644
--- a/activestorage/test/dummy/config/storage.yml
+++ b/activestorage/test/dummy/config/storage.yml
@@ -1,4 +1,3 @@
 local:
   service: Disk
   root: <%= Rails.root.join("storage") %>
-  host: http://localhost:3000
diff --git a/activestorage/test/fixtures/files/favicon.ico b/activestorage/test/fixtures/files/favicon.ico
new file mode 100644
index 0000000000..87192a8a07
--- /dev/null
+++ b/activestorage/test/fixtures/files/favicon.ico
diff --git a/activestorage/test/fixtures/files/racecar_rotated.jpg b/activestorage/test/fixtures/files/racecar_rotated.jpg
new file mode 100644
index 0000000000..89e6d54f98
--- /dev/null
+++ b/activestorage/test/fixtures/files/racecar_rotated.jpg
diff --git a/activestorage/test/fixtures/files/video_with_rectangular_samples.mp4 b/activestorage/test/fixtures/files/video_with_rectangular_samples.mp4
new file mode 100644
index 0000000000..12b04afc87
--- /dev/null
+++ b/activestorage/test/fixtures/files/video_with_rectangular_samples.mp4
diff --git a/activestorage/test/fixtures/files/video_with_undefined_display_aspect_ratio.mp4 b/activestorage/test/fixtures/files/video_with_undefined_display_aspect_ratio.mp4
new file mode 100644
index 0000000000..eb354e756f
--- /dev/null
+++ b/activestorage/test/fixtures/files/video_with_undefined_display_aspect_ratio.mp4
diff --git a/activestorage/test/models/attachments_test.rb b/activestorage/test/models/attachments_test.rb
index f0aa96b411..9ba2759893 100644
--- a/activestorage/test/models/attachments_test.rb
+++ b/activestorage/test/models/attachments_test.rb
@@ -65,14 +65,14 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
       end
     end
 
-    assert user.avatar.attached?
+    assert_predicate user.avatar, :attached?
     assert_equal "funky.jpg", user.avatar.filename.to_s
 
     assert_difference -> { ActiveStorage::Attachment.count }, +1 do
       user.save!
     end
 
-    assert user.reload.avatar.attached?
+    assert_predicate user.reload.avatar, :attached?
     assert_equal "funky.jpg", user.avatar.filename.to_s
   end
 
@@ -81,12 +81,12 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
       @user = User.new(name: "Jason", avatar: { io: StringIO.new("STUFF"), filename: "town.jpg", content_type: "image/jpg" })
     end
 
-    assert @user.new_record?
-    assert @user.avatar.attached?
+    assert_predicate @user, :new_record?
+    assert_predicate @user.avatar, :attached?
     assert_equal "town.jpg", @user.avatar.filename.to_s
 
     @user.save!
-    assert @user.reload.avatar.attached?
+    assert_predicate @user.reload.avatar, :attached?
     assert_equal "town.jpg", @user.avatar.filename.to_s
   end
 
@@ -106,12 +106,12 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     @user.avatar.attach(blob)
 
     assert_equal "image/jpeg", @user.avatar.reload.content_type
-    assert @user.avatar.identified?
+    assert_predicate @user.avatar, :identified?
   end
 
   test "identify newly-attached blob only once" do
     blob = create_file_blob
-    assert blob.identified?
+    assert_predicate blob, :identified?
 
     # The blob's backing file is a PNG image. Fudge its content type so we can tell if it's identified when we attach it.
     blob.update! content_type: "application/octet-stream"
@@ -136,7 +136,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
       @user.avatar.attach blob
     end
 
-    assert blob.reload.analyzed?
+    assert_predicate blob.reload, :analyzed?
 
     @user.avatar.detach
 
@@ -161,7 +161,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     avatar_key = @user.avatar.key
 
     @user.avatar.detach
-    assert_not @user.avatar.attached?
+    assert_not_predicate @user.avatar, :attached?
     assert ActiveStorage::Blob.exists?(avatar_blob_id)
     assert ActiveStorage::Blob.service.exist?(avatar_key)
   end
@@ -171,7 +171,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     avatar_key = @user.avatar.key
 
     @user.avatar.purge
-    assert_not @user.avatar.attached?
+    assert_not_predicate @user.avatar, :attached?
     assert_not ActiveStorage::Blob.service.exist?(avatar_key)
   end
 
@@ -228,7 +228,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
       end
     end
 
-    assert user.highlights.attached?
+    assert_predicate user.highlights, :attached?
     assert_equal "town.jpg", user.highlights.first.filename.to_s
     assert_equal "country.jpg", user.highlights.second.filename.to_s
 
@@ -236,7 +236,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
       user.save!
     end
 
-    assert user.reload.highlights.attached?
+    assert_predicate user.reload.highlights, :attached?
     assert_equal "town.jpg", user.highlights.first.filename.to_s
     assert_equal "country.jpg", user.highlights.second.filename.to_s
   end
@@ -248,13 +248,13 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
         { io: StringIO.new("IT"), filename: "country.jpg", content_type: "image/jpg" }])
     end
 
-    assert @user.new_record?
-    assert @user.highlights.attached?
+    assert_predicate @user, :new_record?
+    assert_predicate @user.highlights, :attached?
     assert_equal "town.jpg", @user.highlights.first.filename.to_s
     assert_equal "country.jpg", @user.highlights.second.filename.to_s
 
     @user.save!
-    assert @user.reload.highlights.attached?
+    assert_predicate @user.reload.highlights, :attached?
     assert_equal "town.jpg", @user.highlights.first.filename.to_s
     assert_equal "country.jpg", @user.highlights.second.filename.to_s
   end
@@ -334,7 +334,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     highlight_keys = @user.highlights.collect(&:key)
 
     @user.highlights.detach
-    assert_not @user.highlights.attached?
+    assert_not_predicate @user.highlights, :attached?
 
     assert ActiveStorage::Blob.exists?(highlight_blob_ids.first)
     assert ActiveStorage::Blob.exists?(highlight_blob_ids.second)
@@ -348,7 +348,7 @@ class ActiveStorage::AttachmentsTest < ActiveSupport::TestCase
     highlight_keys = @user.highlights.collect(&:key)
 
     @user.highlights.purge
-    assert_not @user.highlights.attached?
+    assert_not_predicate @user.highlights, :attached?
     assert_not ActiveStorage::Blob.service.exist?(highlight_keys.first)
     assert_not ActiveStorage::Blob.service.exist?(highlight_keys.second)
   end
diff --git a/activestorage/test/models/blob_test.rb b/activestorage/test/models/blob_test.rb
index b5daee2b57..779e47ffb6 100644
--- a/activestorage/test/models/blob_test.rb
+++ b/activestorage/test/models/blob_test.rb
@@ -2,8 +2,28 @@
 
 require "test_helper"
 require "database/setup"
+require "active_support/testing/method_call_assertions"
 
 class ActiveStorage::BlobTest < ActiveSupport::TestCase
+  include ActiveSupport::Testing::MethodCallAssertions
+
+  test ".unattached scope returns not attached blobs" do
+    class UserWithHasOneAttachedDependentFalse < User
+      has_one_attached :avatar, dependent: false
+    end
+
+    ActiveStorage::Blob.delete_all
+    blob_1 = create_blob filename: "funky.jpg"
+    blob_2 = create_blob filename: "town.jpg"
+
+    user = UserWithHasOneAttachedDependentFalse.create!
+    user.avatar.attach blob_1
+
+    assert_equal [blob_2], ActiveStorage::Blob.unattached
+    user.destroy
+    assert_equal [blob_1, blob_2].map(&:id).sort, ActiveStorage::Blob.unattached.pluck(:id).sort
+  end
+
   test "create after upload sets byte size and checksum" do
     data = "Hello world!"
     blob = create_blob data: data
@@ -23,10 +43,22 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     assert_equal "text/plain", blob.content_type
   end
 
+  test "image?" do
+    blob = create_file_blob filename: "racecar.jpg"
+    assert_predicate blob, :image?
+    assert_not_predicate blob, :audio?
+  end
+
+  test "video?" do
+    blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
+    assert_predicate blob, :video?
+    assert_not_predicate blob, :audio?
+  end
+
   test "text?" do
     blob = create_blob data: "Hello world!"
-    assert blob.text?
-    assert_not blob.audio?
+    assert_predicate blob, :text?
+    assert_not_predicate blob, :audio?
   end
 
   test "download yields chunks" do
@@ -67,6 +99,25 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     freeze_time do
       assert_equal expected_url_for(blob), blob.service_url
       assert_equal expected_url_for(blob, filename: new_filename), blob.service_url(filename: new_filename)
+      assert_equal expected_url_for(blob, filename: new_filename), blob.service_url(filename: "new.txt")
+      assert_equal expected_url_for(blob, filename: blob.filename), blob.service_url(filename: nil)
+    end
+  end
+
+  test "urls allow for custom options" do
+    blob = create_blob(filename: "original.txt")
+
+    options = [
+      blob.key,
+      expires_in: blob.service.url_expires_in,
+      disposition: :inline,
+      content_type: blob.content_type,
+      filename: blob.filename,
+      thumb_size: "300x300",
+      thumb_mode: "crop"
+    ]
+    assert_called_with(blob.service, :url, options) do
+      blob.service_url(thumb_size: "300x300", thumb_mode: "crop")
     end
   end
 
diff --git a/activestorage/test/models/preview_test.rb b/activestorage/test/models/preview_test.rb
index b0c6d2c45b..55fdc228c8 100644
--- a/activestorage/test/models/preview_test.rb
+++ b/activestorage/test/models/preview_test.rb
@@ -8,7 +8,7 @@ class ActiveStorage::PreviewTest < ActiveSupport::TestCase
     blob = create_file_blob(filename: "report.pdf", content_type: "application/pdf")
     preview = blob.preview(resize: "640x280").processed
 
-    assert preview.image.attached?
+    assert_predicate preview.image, :attached?
     assert_equal "report.png", preview.image.filename.to_s
     assert_equal "image/png", preview.image.content_type
 
@@ -21,7 +21,7 @@ class ActiveStorage::PreviewTest < ActiveSupport::TestCase
     blob = create_file_blob(filename: "video.mp4", content_type: "video/mp4")
     preview = blob.preview(resize: "640x280").processed
 
-    assert preview.image.attached?
+    assert_predicate preview.image, :attached?
     assert_equal "video.png", preview.image.filename.to_s
     assert_equal "image/png", preview.image.content_type
 
diff --git a/activestorage/test/models/variant_test.rb b/activestorage/test/models/variant_test.rb
index 0cf8a583bd..0f3ada25c0 100644
--- a/activestorage/test/models/variant_test.rb
+++ b/activestorage/test/models/variant_test.rb
@@ -50,6 +50,17 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
     assert_equal 20, image.height
   end
 
+  test "resized variation of ICO blob" do
+    blob = create_file_blob(filename: "favicon.ico", content_type: "image/vnd.microsoft.icon")
+    variant = blob.variant(resize: "20x20").processed
+    assert_match(/icon\.png/, variant.service_url)
+
+    image = read_image(variant)
+    assert_equal "PNG", image.type
+    assert_equal 20, image.width
+    assert_equal 20, image.height
+  end
+
   test "optimized variation of GIF blob" do
     blob = create_file_blob(filename: "image.gif", content_type: "image/gif")
 
diff --git a/activestorage/test/service/configurator_test.rb b/activestorage/test/service/configurator_test.rb
index 0a79b37aa4..fe8a637ad0 100644
--- a/activestorage/test/service/configurator_test.rb
+++ b/activestorage/test/service/configurator_test.rb
@@ -4,7 +4,7 @@ require "service/shared_service_tests"
 
 class ActiveStorage::Service::ConfiguratorTest < ActiveSupport::TestCase
   test "builds correct service instance based on service name" do
-    service = ActiveStorage::Service::Configurator.build(:foo, foo: { service: "Disk", root: "path", host: "http://localhost:3000" })
+    service = ActiveStorage::Service::Configurator.build(:foo, foo: { service: "Disk", root: "path" })
 
     assert_instance_of ActiveStorage::Service::DiskService, service
     assert_equal "path", service.root
diff --git a/activestorage/test/service/disk_service_test.rb b/activestorage/test/service/disk_service_test.rb
index f0171f8999..4a6361b920 100644
--- a/activestorage/test/service/disk_service_test.rb
+++ b/activestorage/test/service/disk_service_test.rb
@@ -3,7 +3,7 @@
 require "service/shared_service_tests"
 
 class ActiveStorage::Service::DiskServiceTest < ActiveSupport::TestCase
-  SERVICE = ActiveStorage::Service::DiskService.new(root: File.join(Dir.tmpdir, "active_storage"), host: "http://localhost:3000")
+  SERVICE = ActiveStorage::Service::DiskService.new(root: File.join(Dir.tmpdir, "active_storage"))
 
   include ActiveStorage::Service::SharedServiceTests
 
diff --git a/activestorage/test/service/mirror_service_test.rb b/activestorage/test/service/mirror_service_test.rb
index 6b601f3b2b..87306644c5 100644
--- a/activestorage/test/service/mirror_service_test.rb
+++ b/activestorage/test/service/mirror_service_test.rb
@@ -6,13 +6,12 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   mirror_config = (1..3).map do |i|
     [ "mirror_#{i}",
       service: "Disk",
-      root: Dir.mktmpdir("active_storage_tests_mirror_#{i}"),
-      host: "http://localhost:3000" ]
+      root: Dir.mktmpdir("active_storage_tests_mirror_#{i}") ]
   end.to_h
 
   config = mirror_config.merge \
     mirror:  { service: "Mirror", primary: "primary", mirrors: mirror_config.keys },
-    primary: { service: "Disk", root: Dir.mktmpdir("active_storage_tests_primary"), host: "http://localhost:3000" }
+    primary: { service: "Disk", root: Dir.mktmpdir("active_storage_tests_primary") }
 
   SERVICE = ActiveStorage::Service.configure :mirror, config
 
@@ -20,11 +19,16 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
 
   test "uploading to all services" do
     begin
-      data = "Something else entirely!"
-      key  = upload(data, to: @service)
+      key      = SecureRandom.base58(24)
+      data     = "Something else entirely!"
+      io       = StringIO.new(data)
+      checksum = Digest::MD5.base64digest(data)
 
-      assert_equal data, SERVICE.primary.download(key)
-      SERVICE.mirrors.each do |mirror|
+      @service.upload key, io.tap(&:read), checksum: checksum
+      assert_predicate io, :eof?
+
+      assert_equal data, @service.primary.download(key)
+      @service.mirrors.each do |mirror|
         assert_equal data, mirror.download(key)
       end
     ensure
@@ -33,14 +37,18 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
   end
 
   test "downloading from primary service" do
-    data = "Something else entirely!"
-    key  = upload(data, to: SERVICE.primary)
+    key      = SecureRandom.base58(24)
+    data     = "Something else entirely!"
+    checksum = Digest::MD5.base64digest(data)
+
+    @service.primary.upload key, StringIO.new(data), checksum: checksum
 
     assert_equal data, @service.download(key)
   end
 
   test "deleting from all services" do
     @service.delete FIXTURE_KEY
+
     assert_not SERVICE.primary.exist?(FIXTURE_KEY)
     SERVICE.mirrors.each do |mirror|
       assert_not mirror.exist?(FIXTURE_KEY)
@@ -51,17 +59,8 @@ class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
     filename = ActiveStorage::Filename.new("test.txt")
 
     freeze_time do
-      assert_equal SERVICE.primary.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain"),
+      assert_equal @service.primary.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain"),
         @service.url(FIXTURE_KEY, expires_in: 2.minutes, disposition: :inline, filename: filename, content_type: "text/plain")
     end
   end
-
-  private
-    def upload(data, to:)
-      SecureRandom.base58(24).tap do |key|
-        io = StringIO.new(data).tap(&:read)
-        @service.upload key, io, checksum: Digest::MD5.base64digest(data)
-        assert io.eof?
-      end
-    end
 end
diff --git a/activestorage/test/service/s3_service_test.rb b/activestorage/test/service/s3_service_test.rb
index c3818422aa..d6996209d2 100644
--- a/activestorage/test/service/s3_service_test.rb
+++ b/activestorage/test/service/s3_service_test.rb
@@ -35,7 +35,7 @@ if SERVICE_CONFIGURATIONS[:s3] && SERVICE_CONFIGURATIONS[:s3][:access_key_id].pr
       url = @service.url(FIXTURE_KEY, expires_in: 5.minutes,
         disposition: :inline, filename: ActiveStorage::Filename.new("avatar.png"), content_type: "image/png")
 
-      assert_match(/s3\.(\S+)?amazonaws.com.*response-content-disposition=inline.*avatar\.png.*response-content-type=image%2Fpng/, url)
+      assert_match(/s3(-[-a-z0-9]+)?\.(\S+)?amazonaws.com.*response-content-disposition=inline.*avatar\.png.*response-content-type=image%2Fpng/, url)
       assert_match SERVICE_CONFIGURATIONS[:s3][:bucket], url
     end
 
diff --git a/activestorage/test/template/image_tag_test.rb b/activestorage/test/template/image_tag_test.rb
index 80f183e0e3..f0b166c225 100644
--- a/activestorage/test/template/image_tag_test.rb
+++ b/activestorage/test/template/image_tag_test.rb
@@ -33,7 +33,7 @@ class ActiveStorage::ImageTagTest < ActionView::TestCase
   test "error when attachment's empty" do
     @user = User.create!(name: "DHH")
 
-    assert_not @user.avatar.attached?
+    assert_not_predicate @user.avatar, :attached?
     assert_raises(ArgumentError) { image_tag(@user.avatar) }
   end
 
diff --git a/activestorage/test/test_helper.rb b/activestorage/test/test_helper.rb
index 51f8ebad18..98fa44a604 100644
--- a/activestorage/test/test_helper.rb
+++ b/activestorage/test/test_helper.rb
@@ -34,7 +34,7 @@ rescue Errno::ENOENT
 end
 
 require "tmpdir"
-ActiveStorage::Blob.service = ActiveStorage::Service::DiskService.new(root: Dir.mktmpdir("active_storage_tests"), host: "http://localhost:3000")
+ActiveStorage::Blob.service = ActiveStorage::Service::DiskService.new(root: Dir.mktmpdir("active_storage_tests"))
 
 ActiveStorage.logger = ActiveSupport::Logger.new(nil)
 ActiveStorage.verifier = ActiveSupport::MessageVerifier.new("Testing")
diff --git a/activesupport/.gitignore b/activesupport/.gitignore
new file mode 100644
index 0000000000..8cde8514fd
--- /dev/null
+++ b/activesupport/.gitignore
@@ -0,0 +1 @@
+/test/fixtures/isolation_test/
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index a21a817fbb..db53c151ea 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,496 +1,56 @@
-*   Add missing instrumentation for `read_multi` in `ActiveSupport::Cache::Store`.
+## Rails 6.0.0.alpha (Unreleased) ##
 
-    *Ignatius Reza Lesmana*
+*   Caching: MemCache and Redis `read_multi` and `fetch_multi` speedup.
+    Read from the local in-memory cache before consulting the backend.
 
-*   `assert_changes` will always assert that the expression changes,
-    regardless of `from:` and `to:` argument combinations.
+    *Gabriel Sobrinho*
 
-    *Daniel Ma*
+*   Return all mappings for a timezone identifier in `country_zones`
 
-*   Use SHA-1 to generate non-sensitive digests, such as the ETag header.
+    Some timezones like `Europe/London` have multiple mappings in
+    `ActiveSupport::TimeZone::MAPPING` so return all of them instead
+    of the first one found by using `Hash#value`. e.g:
 
-    Enabled by default for new apps; upgrading apps can opt in by setting
-    `config.active_support.use_sha1_digests = true`.
+        # Before
+        ActiveSupport::TimeZone.country_zones("GB") # => ["Edinburgh"]
 
-    *Dmitri Dolguikh*, *Eugene Kenny*
+        # After
+        ActiveSupport::TimeZone.country_zones("GB") # => ["Edinburgh", "London"]
 
-
-## Rails 5.2.0.beta2 (November 28, 2017) ##
-
-*   No changes.
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Changed default behaviour of `ActiveSupport::SecurityUtils.secure_compare`,
-    to make it not leak length information even for variable length string.
-
-    Renamed old `ActiveSupport::SecurityUtils.secure_compare` to `fixed_length_secure_compare`,
-    and started raising `ArgumentError` in case of length mismatch of passed strings.
-
-    *Vipul A M*
-
-*   Make `ActiveSupport::TimeZone.all` return only time zones that are in
-    `ActiveSupport::TimeZone::MAPPING`.
-
-    Fixes #7245.
-
-    *Chris LaRose*
-
-*   MemCacheStore: Support expiring counters.
-
-    Pass `expires_in: [seconds]` to `#increment` and `#decrement` options
-    to set the Memcached TTL (time-to-live) if the counter doesn't exist.
-    If the counter exists, Memcached doesn't extend its expiry when it's
-    incremented or decremented.
-
-    ```
-    Rails.cache.increment("my_counter", 1, expires_in: 2.minutes)
-    ```
-
-    *Takumasa Ochi*
-
-*   Handle `TZInfo::AmbiguousTime` errors
-
-    Make `ActiveSupport::TimeWithZone` match Ruby's handling of ambiguous
-    times by choosing the later period, e.g.
-
-    Ruby:
-    ```
-    ENV["TZ"] = "Europe/Moscow"
-    Time.local(2014, 10, 26, 1, 0, 0)   # => 2014-10-26 01:00:00 +0300
-    ```
-
-    Before:
-    ```
-    >> "2014-10-26 01:00:00".in_time_zone("Moscow")
-    TZInfo::AmbiguousTime: 26/10/2014 01:00 is an ambiguous local time.
-    ```
-
-    After:
-    ```
-    >> "2014-10-26 01:00:00".in_time_zone("Moscow")
-    => Sun, 26 Oct 2014 01:00:00 MSK +03:00
-    ```
-
-    Fixes #17395.
+    Fixes #31668.
 
     *Andrew White*
 
-*   Redis cache store.
-
-    ```
-    # Defaults to `redis://localhost:6379/0`. Only use for dev/test.
-    config.cache_store = :redis_cache_store
-
-    # Supports all common cache store options (:namespace, :compress,
-    # :compress_threshold, :expires_in, :race_condition_ttl) and all
-    # Redis options.
-    cache_password = Rails.application.secrets.redis_cache_password
-    config.cache_store = :redis_cache_store, driver: :hiredis,
-      namespace: 'myapp-cache', compress: true, timeout: 1,
-      url: "redis://:#{cache_password}@myapp-cache-1:6379/0"
-
-    # Supports Redis::Distributed with multiple hosts
-    config.cache_store = :redis_cache_store, driver: :hiredis
-      namespace: 'myapp-cache', compress: true,
-      url: %w[
-        redis://myapp-cache-1:6379/0
-        redis://myapp-cache-1:6380/0
-        redis://myapp-cache-2:6379/0
-        redis://myapp-cache-2:6380/0
-        redis://myapp-cache-3:6379/0
-        redis://myapp-cache-3:6380/0
-      ]
-
-    # Or pass a builder block
-    config.cache_store = :redis_cache_store,
-      namespace: 'myapp-cache', compress: true,
-      redis: -> { Redis.new … }
-    ```
-
-    Deployment note: Take care to use a *dedicated Redis cache* rather
-    than pointing this at your existing Redis server. It won't cope well
-    with mixed usage patterns and it won't expire cache entries by default.
-
-    Redis cache server setup guide: https://redis.io/topics/lru-cache
-
-    *Jeremy Daer*
-
-*   Cache: Enable compression by default for values > 1kB.
-
-    Compression has long been available, but opt-in and at a 16kB threshold.
-    It wasn't enabled by default due to CPU cost. Today it's cheap and typical
-    cache data is eminently compressible, such as HTML or JSON fragments.
-    Compression dramatically reduces Memcached/Redis mem usage, which means
-    the same cache servers can store more data, which means higher hit rates.
-
-    To disable compression, pass `compress: false` to the initializer.
+*   `String#truncate_bytes` to truncate a string to a maximum bytesize without
+    breaking multibyte characters or grapheme clusters like 👩‍👩‍👦‍👦.
 
     *Jeremy Daer*
 
-*   Allow `Range#include?` on TWZ ranges
-
-    In #11474 we prevented TWZ ranges being iterated over which matched
-    Ruby's handling of Time ranges and as a consequence `include?`
-    stopped working with both Time ranges and TWZ ranges. However in
-    ruby/ruby@b061634 support was added for `include?` to use `cover?`
-    for 'linear' objects. Since we have no way of making Ruby consider
-    TWZ instances as 'linear' we have to override `Range#include?`.
-
-    Fixes #30799.
-
-    *Andrew White*
-
-*   Fix acronym support in `humanize`
-
-    Acronym inflections are stored with lowercase keys in the hash but
-    the match wasn't being lowercased before being looked up in the hash.
-    This shouldn't have any performance impact because before it would
-    fail to find the acronym and perform the `downcase` operation anyway.
-
-    Fixes #31052.
-
-    *Andrew White*
-
-*   Add same method signature for `Time#prev_year` and `Time#next_year`
-    in accordance with `Date#prev_year`, `Date#next_year`.
-
-    Allows pass argument for `Time#prev_year` and `Time#next_year`.
-
-    Before:
-    ```
-    Time.new(2017, 9, 16, 17, 0).prev_year    # => 2016-09-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).prev_year(1)
-    # => ArgumentError: wrong number of arguments (given 1, expected 0)
-
-    Time.new(2017, 9, 16, 17, 0).next_year    # => 2018-09-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).next_year(1)
-    # => ArgumentError: wrong number of arguments (given 1, expected 0)
-    ```
-
-    After:
-    ```
-    Time.new(2017, 9, 16, 17, 0).prev_year    # => 2016-09-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).prev_year(1) # => 2016-09-16 17:00:00 +0300
-
-    Time.new(2017, 9, 16, 17, 0).next_year    # => 2018-09-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).next_year(1) # => 2018-09-16 17:00:00 +0300
-    ```
-
-    *bogdanvlviv*
-
-*   Add same method signature for `Time#prev_month` and `Time#next_month`
-    in accordance with `Date#prev_month`, `Date#next_month`.
-
-    Allows pass argument for `Time#prev_month` and `Time#next_month`.
-
-    Before:
-    ```
-    Time.new(2017, 9, 16, 17, 0).prev_month    # => 2017-08-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).prev_month(1)
-    # => ArgumentError: wrong number of arguments (given 1, expected 0)
-
-    Time.new(2017, 9, 16, 17, 0).next_month    # => 2017-10-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).next_month(1)
-    # => ArgumentError: wrong number of arguments (given 1, expected 0)
-    ```
-
-    After:
-    ```
-    Time.new(2017, 9, 16, 17, 0).prev_month    # => 2017-08-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).prev_month(1) # => 2017-08-16 17:00:00 +0300
-
-    Time.new(2017, 9, 16, 17, 0).next_month    # => 2017-10-16 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).next_month(1) # => 2017-10-16 17:00:00 +0300
-    ```
-
-    *bogdanvlviv*
-
-*   Add same method signature for `Time#prev_day` and `Time#next_day`
-    in accordance with `Date#prev_day`, `Date#next_day`.
-
-    Allows pass argument for `Time#prev_day` and `Time#next_day`.
-
-    Before:
-    ```
-    Time.new(2017, 9, 16, 17, 0).prev_day    # => 2017-09-15 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).prev_day(1)
-    # => ArgumentError: wrong number of arguments (given 1, expected 0)
-
-    Time.new(2017, 9, 16, 17, 0).next_day    # => 2017-09-17 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).next_day(1)
-    # => ArgumentError: wrong number of arguments (given 1, expected 0)
-    ```
-
-    After:
-    ```
-    Time.new(2017, 9, 16, 17, 0).prev_day    # => 2017-09-15 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).prev_day(1) # => 2017-09-15 17:00:00 +0300
-
-    Time.new(2017, 9, 16, 17, 0).next_day    # => 2017-09-17 17:00:00 +0300
-    Time.new(2017, 9, 16, 17, 0).next_day(1) # => 2017-09-17 17:00:00 +0300
-    ```
-
-    *bogdanvlviv*
-
-*   `IO#to_json` now returns the `to_s` representation, rather than
-    attempting to convert to an array. This fixes a bug where `IO#to_json`
-    would raise an `IOError` when called on an unreadable object.
-
-    Fixes #26132.
-
-    *Paul Kuruvilla*
-
-*   Remove deprecated `halt_callback_chains_on_return_false` option.
-
-    *Rafael Mendonça França*
-
-*   Remove deprecated `:if` and `:unless` string filter for callbacks.
-
-    *Rafael Mendonça França*
-
-*   `Hash#slice` now falls back to Ruby 2.5+'s built-in definition if defined.
-
-    *Akira Matsuda*
-
-*   Deprecate `secrets.secret_token`.
-
-    The architecture for secrets had a big upgrade between Rails 3 and Rails 4,
-    when the default changed from using `secret_token` to `secret_key_base`.
-
-    `secret_token` has been soft deprecated in documentation for four years
-    but is still in place to support apps created before Rails 4.
-    Deprecation warnings have been added to help developers upgrade their
-    applications to `secret_key_base`.
-
-    *claudiob*, *Kasper Timm Hansen*
-
-*   Return an instance of `HashWithIndifferentAccess` from `HashWithIndifferentAccess#transform_keys`.
-
-    *Yuji Yaginuma*
-
-*   Add key rotation support to `MessageEncryptor` and `MessageVerifier`
-
-    This change introduces a `rotate` method to both the `MessageEncryptor` and
-    `MessageVerifier` classes. This method accepts the same arguments and
-    options as the given classes' constructor. The `encrypt_and_verify` method
-    for `MessageEncryptor` and the `verified` method for `MessageVerifier` also
-    accept an optional keyword argument `:on_rotation` block which is called
-    when a rotated instance is used to decrypt or verify the message.
-
-    *Michael J Coyne*
-
-*   Deprecate `Module#reachable?` method.
+*   `String#strip_heredoc` preserves frozenness.
 
-    *bogdanvlviv*
+        "foo".freeze.strip_heredoc.frozen?  # => true
 
-*   Add `config/credentials.yml.enc` to store production app secrets.
+    Fixes that frozen string literals would inadvertently become unfrozen:
 
-    Allows saving any authentication credentials for third party services
-    directly in repo encrypted with `config/master.key` or `ENV["RAILS_MASTER_KEY"]`.
+        # frozen_string_literal: true
 
-    This will eventually replace `Rails.application.secrets` and the encrypted
-    secrets introduced in Rails 5.1.
+        foo = <<-MSG.strip_heredoc
+          la la la
+        MSG
 
-    *DHH*, *Kasper Timm Hansen*
-
-*   Add `ActiveSupport::EncryptedFile` and `ActiveSupport::EncryptedConfiguration`.
-
-    Allows for stashing encrypted files or configuration directly in repo by
-    encrypting it with a key.
-
-    Backs the new credentials setup above, but can also be used independently.
-
-    *DHH*, *Kasper Timm Hansen*
-
-*   `Module#delegate_missing_to` now raises `DelegationError` if target is nil,
-    similar to `Module#delegate`.
-
-    *Anton Khamets*
-
-*   Update `String#camelize` to provide feedback when wrong option is passed
-
-    `String#camelize` was returning nil without any feedback when an
-    invalid option was passed as a parameter.
-
-    Previously:
-
-        'one_two'.camelize(true)
-        # => nil
-
-    Now:
-
-        'one_two'.camelize(true)
-        # => ArgumentError: Invalid option, use either :upper or :lower.
-
-    *Ricardo Díaz*
-
-*   Fix modulo operations involving durations
-
-    Rails 5.1 introduced `ActiveSupport::Duration::Scalar` as a wrapper
-    around numeric values as a way of ensuring a duration was the outcome of
-    an expression. However, the implementation was missing support for modulo
-    operations. This support has now been added and should result in a duration
-    being returned from expressions involving modulo operations.
-
-    Prior to Rails 5.1:
-
-        5.minutes % 2.minutes
-        # => 60
-
-    Now:
-
-        5.minutes % 2.minutes
-        # => 1 minute
-
-    Fixes #29603 and #29743.
-
-    *Sayan Chakraborty*, *Andrew White*
-
-*   Fix division where a duration is the denominator
-
-    PR #29163 introduced a change in behavior when a duration was the denominator
-    in a calculation - this was incorrect as dividing by a duration should always
-    return a `Numeric`. The behavior of previous versions of Rails has been restored.
-
-    Fixes #29592.
-
-    *Andrew White*
-
-*   Add purpose and expiry support to `ActiveSupport::MessageVerifier` &
-   `ActiveSupport::MessageEncryptor`.
-
-    For instance, to ensure a message is only usable for one intended purpose:
-
-        token = @verifier.generate("x", purpose: :shipping)
-
-        @verifier.verified(token, purpose: :shipping) # => "x"
-        @verifier.verified(token)                     # => nil
-
-    Or make it expire after a set time:
-
-        @verifier.generate("x", expires_in: 1.month)
-        @verifier.generate("y", expires_at: Time.now.end_of_year)
-
-    Showcased with `ActiveSupport::MessageVerifier`, but works the same for
-    `ActiveSupport::MessageEncryptor`'s `encrypt_and_sign` and `decrypt_and_verify`.
-
-    Pull requests: #29599, #29854
-
-    *Assain Jaleel*
-
-*   Make the order of `Hash#reverse_merge!` consistent with `HashWithIndifferentAccess`.
-
-    *Erol Fornoles*
-
-*   Add `freeze_time` helper which freezes time to `Time.now` in tests.
-
-    *Prathamesh Sonpatki*
-
-*   Default `ActiveSupport::MessageEncryptor` to use AES 256 GCM encryption.
-
-    On for new Rails 5.2 apps. Upgrading apps can find the config as a new
-    framework default.
-
-    *Assain Jaleel*
-
-*   Cache: `write_multi`
-
-        Rails.cache.write_multi foo: 'bar', baz: 'qux'
-
-    Plus faster fetch_multi with stores that implement `write_multi_entries`.
-    Keys that aren't found may be written to the cache store in one shot
-    instead of separate writes.
-
-    The default implementation simply calls `write_entry` for each entry.
-    Stores may override if they're capable of one-shot bulk writes, like
-    Redis `MSET`.
+        foo.frozen?  # => false !??
 
     *Jeremy Daer*
 
-*   Add default option to module and class attribute accessors.
-
-        mattr_accessor :settings, default: {}
-
-    Works for `mattr_reader`, `mattr_writer`, `cattr_accessor`, `cattr_reader`,
-    and `cattr_writer` as well.
-
-    *Genadi Samokovarov*
-
-*   Add `Date#prev_occurring` and `Date#next_occurring` to return specified next/previous occurring day of week.
-
-    *Shota Iguchi*
-
-*   Add default option to `class_attribute`.
-
-    Before:
-
-        class_attribute :settings
-        self.settings = {}
-
-    Now:
-
-        class_attribute :settings, default: {}
-
-    *DHH*
-
-*   `#singularize` and `#pluralize` now respect uncountables for the specified locale.
-
-    *Eilis Hamilton*
-
-*   Add `ActiveSupport::CurrentAttributes` to provide a thread-isolated attributes singleton.
-    Primary use case is keeping all the per-request attributes easily available to the whole system.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
-    *DHH*
-
-*   Fix implicit coercion calculations with scalars and durations
-
-    Previously, calculations where the scalar is first would be converted to a duration
-    of seconds, but this causes issues with dates being converted to times, e.g:
-
-        Time.zone = "Beijing"           # => Asia/Shanghai
-        date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
-        2 * 1.day                       # => 172800 seconds
-        date + 2 * 1.day                # => Mon, 22 May 2017 00:00:00 CST +08:00
-
-    Now, the `ActiveSupport::Duration::Scalar` calculation methods will try to maintain
-    the part structure of the duration where possible, e.g:
-
-        Time.zone = "Beijing"           # => Asia/Shanghai
-        date = Date.civil(2017, 5, 20)  # => Mon, 20 May 2017
-        2 * 1.day                       # => 2 days
-        date + 2 * 1.day                # => Mon, 22 May 2017
-
-    Fixes #29160, #28970.
-
-    *Andrew White*
-
-*   Add support for versioned cache entries. This enables the cache stores to recycle cache keys, greatly saving
-    on storage in cases with frequent churn. Works together with the separation of `#cache_key` and `#cache_version`
-    in Active Record and its use in Action Pack's fragment caching.
-
-    *DHH*
-
-*   Pass gem name and deprecation horizon to deprecation notifications.
-
-    *Willem van Bergen*
-
-*   Add support for `:offset` and `:zone` to `ActiveSupport::TimeWithZone#change`
-
-    *Andrew White*
-
-*   Add support for `:offset` to `Time#change`
-
-    Fixes #28723.
-
-    *Andrew White*
+    *Jeremy Daer*
 
-*   Add `fetch_values` for `HashWithIndifferentAccess`
+*   Adds parallel testing to Rails
 
-    The method was originally added to `Hash` in Ruby 2.3.0.
+    Parallelize your test suite with forked processes or threads.
 
-    *Josh Pencheon*
+    *Eileen M. Uchitelle*, *Aaron Patterson*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/activesupport/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/activesupport/CHANGELOG.md) for previous changes.
diff --git a/activesupport/Rakefile b/activesupport/Rakefile
index 8672ab1542..f10f19be0a 100644
--- a/activesupport/Rakefile
+++ b/activesupport/Rakefile
@@ -14,10 +14,30 @@ Rake::TestTask.new do |t|
   t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
 end
 
+Rake::Task[:test].enhance do
+  Rake::Task["test:cache_stores:redis:ruby"].invoke
+end
+
 namespace :test do
   task :isolated do
     Dir.glob("test/**/*_test.rb").all? do |file|
       sh(Gem.ruby, "-w", "-Ilib:test", file)
     end || raise("Failures")
   end
+
+  namespace :cache_stores do
+    namespace :redis do
+      %w[ ruby hiredis ].each do |driver|
+        task("env:#{driver}") { ENV["REDIS_DRIVER"] = driver }
+
+        Rake::TestTask.new(driver => "env:#{driver}") do |t|
+          t.libs << "test"
+          t.test_files = ["test/cache/stores/redis_cache_store_test.rb"]
+          t.warning = true
+          t.verbose = true
+          t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
+        end
+      end
+    end
+  end
 end
diff --git a/activesupport/activesupport.gemspec b/activesupport/activesupport.gemspec
index db801d2da2..aa695c98b2 100644
--- a/activesupport/activesupport.gemspec
+++ b/activesupport/activesupport.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "A toolkit of support libraries and Ruby core extensions extracted from the Rails framework."
   s.description = "A toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Rich support for multibyte strings, internationalization, time zones, and testing."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
     "changelog_uri"   => "https://github.com/rails/rails/blob/v#{version}/activesupport/CHANGELOG.md"
   }
 
-  s.add_dependency "i18n",       "~> 0.7"
+  s.add_dependency "i18n",       ">= 0.7", "< 2"
   s.add_dependency "tzinfo",     "~> 1.1"
   s.add_dependency "minitest",   "~> 5.1"
   s.add_dependency "concurrent-ruby", "~> 1.0", ">= 1.0.2"
diff --git a/activesupport/bin/generate_tables b/activesupport/bin/generate_tables
deleted file mode 100755
index 18199b2171..0000000000
--- a/activesupport/bin/generate_tables
+++ /dev/null
@@ -1,141 +0,0 @@
-#!/usr/bin/env ruby
-# frozen_string_literal: true
-
-begin
-  $:.unshift(File.expand_path("../lib", __dir__))
-  require "active_support"
-rescue IOError
-end
-
-require "open-uri"
-require "tmpdir"
-require "fileutils"
-
-module ActiveSupport
-  module Multibyte
-    module Unicode
-      class UnicodeDatabase
-        def load; end
-      end
-
-      class DatabaseGenerator
-        BASE_URI = "http://www.unicode.org/Public/#{UNICODE_VERSION}/ucd/"
-        SOURCES = {
-          codepoints: BASE_URI + "UnicodeData.txt",
-          composition_exclusion: BASE_URI + "CompositionExclusions.txt",
-          grapheme_break_property: BASE_URI + "auxiliary/GraphemeBreakProperty.txt",
-          cp1252: "http://unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP1252.TXT"
-        }
-
-        def initialize
-          @ucd = Unicode::UnicodeDatabase.new
-        end
-
-        def parse_codepoints(line)
-          codepoint = Codepoint.new
-          raise "Could not parse input." unless line =~ /^
-            ([0-9A-F]+);        # code
-            ([^;]+);            # name
-            ([A-Z]+);           # general category
-            ([0-9]+);           # canonical combining class
-            ([A-Z]+);           # bidi class
-            (<([A-Z]*)>)?       # decomposition type
-            ((\ ?[0-9A-F]+)*);  # decomposition mapping
-            ([0-9]*);           # decimal digit
-            ([0-9]*);           # digit
-            ([^;]*);            # numeric
-            ([YN]*);            # bidi mirrored
-            ([^;]*);            # unicode 1.0 name
-            ([^;]*);            # iso comment
-            ([0-9A-F]*);        # simple uppercase mapping
-            ([0-9A-F]*);        # simple lowercase mapping
-            ([0-9A-F]*)$/ix     # simple titlecase mapping
-          codepoint.code              = $1.hex
-          codepoint.combining_class   = Integer($4)
-          codepoint.decomp_type       = $7
-          codepoint.decomp_mapping    = ($8 == "") ? nil : $8.split.collect(&:hex)
-          codepoint.uppercase_mapping = ($16 == "") ? 0 : $16.hex
-          codepoint.lowercase_mapping = ($17 == "") ? 0 : $17.hex
-          @ucd.codepoints[codepoint.code] = codepoint
-        end
-
-        def parse_grapheme_break_property(line)
-          if line =~ /^([0-9A-F.]+)\s*;\s*([\w]+)\s*#/
-            type = $2.downcase.intern
-            @ucd.boundary[type] ||= []
-            if $1.include? ".."
-              parts = $1.split ".."
-              @ucd.boundary[type] << (parts[0].hex..parts[1].hex)
-            else
-              @ucd.boundary[type] << $1.hex
-            end
-          end
-        end
-
-        def parse_composition_exclusion(line)
-          if line =~ /^([0-9A-F]+)/i
-            @ucd.composition_exclusion << $1.hex
-          end
-        end
-
-        def parse_cp1252(line)
-          if line =~ /^([0-9A-Fx]+)\s([0-9A-Fx]+)/i
-            @ucd.cp1252[$1.hex] = $2.hex
-          end
-        end
-
-        def create_composition_map
-          @ucd.codepoints.each do |_, cp|
-            if !cp.nil? && cp.combining_class == 0 && cp.decomp_type.nil? && !cp.decomp_mapping.nil? && cp.decomp_mapping.length == 2 && @ucd.codepoints[cp.decomp_mapping[0]].combining_class == 0 && !@ucd.composition_exclusion.include?(cp.code)
-              @ucd.composition_map[cp.decomp_mapping[0]] ||= {}
-              @ucd.composition_map[cp.decomp_mapping[0]][cp.decomp_mapping[1]] = cp.code
-            end
-          end
-        end
-
-        def normalize_boundary_map
-          @ucd.boundary.each do |k, v|
-            if [:lf, :cr].include? k
-              @ucd.boundary[k] = v[0]
-            end
-          end
-        end
-
-        def parse
-          SOURCES.each do |type, url|
-            filename = File.join(Dir.tmpdir, UNICODE_VERSION, "#{url.split('/').last}")
-            unless File.exist?(filename)
-              $stderr.puts "Downloading #{url.split('/').last}"
-              FileUtils.mkdir_p(File.dirname(filename))
-              File.open(filename, "wb") do |target|
-                open(url) do |source|
-                  source.each_line { |line| target.write line }
-                end
-              end
-            end
-            File.open(filename) do |file|
-              file.each_line { |line| send "parse_#{type}".intern, line }
-            end
-          end
-          create_composition_map
-          normalize_boundary_map
-        end
-
-        def dump_to(filename)
-          File.open(filename, "wb") do |f|
-            f.write Marshal.dump([@ucd.codepoints, @ucd.composition_exclusion, @ucd.composition_map, @ucd.boundary, @ucd.cp1252])
-          end
-        end
-      end
-    end
-  end
-end
-
-if __FILE__ == $0
-  filename = ActiveSupport::Multibyte::Unicode::UnicodeDatabase.filename
-  generator = ActiveSupport::Multibyte::Unicode::DatabaseGenerator.new
-  generator.parse
-  print "Writing to: #{filename}"
-  generator.dump_to filename
-  puts " (#{File.size(filename)} bytes)"
-end
diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 2d038dba77..1ea2d0bbf2 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -160,6 +160,23 @@ module ActiveSupport
       attr_reader :silence, :options
       alias :silence? :silence
 
+      class << self
+        private
+          def retrieve_pool_options(options)
+            {}.tap do |pool_options|
+              pool_options[:size] = options.delete(:pool_size) if options[:pool_size]
+              pool_options[:timeout] = options.delete(:pool_timeout) if options[:pool_timeout]
+            end
+          end
+
+          def ensure_connection_pool_added!
+            require "connection_pool"
+          rescue LoadError => e
+            $stderr.puts "You don't have connection_pool installed in your application. Please add it to your Gemfile and run bundle install"
+            raise e
+          end
+      end
+
       # Creates a new cache. The options will be passed to any write method calls
       # except for <tt>:namespace</tt> which can be used to set the global
       # namespace for the cache.
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index 00a3670d64..2840781dde 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -63,7 +63,14 @@ module ActiveSupport
         addresses = addresses.flatten
         options = addresses.extract_options!
         addresses = ["localhost:11211"] if addresses.empty?
-        Dalli::Client.new(addresses, options)
+        pool_options = retrieve_pool_options(options)
+
+        if pool_options.empty?
+          Dalli::Client.new(addresses, options)
+        else
+          ensure_connection_pool_added!
+          ConnectionPool.new(pool_options) { Dalli::Client.new(addresses, options.merge(threadsafe: false)) }
+        end
       end
 
       # Creates a new MemCacheStore object, with the given memcached server
@@ -99,7 +106,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:increment, name, amount: amount) do
           rescue_error_with nil do
-            @data.incr(normalize_key(name, options), amount, options[:expires_in])
+            @data.with { |c| c.incr(normalize_key(name, options), amount, options[:expires_in]) }
           end
         end
       end
@@ -112,7 +119,7 @@ module ActiveSupport
         options = merged_options(options)
         instrument(:decrement, name, amount: amount) do
           rescue_error_with nil do
-            @data.decr(normalize_key(name, options), amount, options[:expires_in])
+            @data.with { |c| c.decr(normalize_key(name, options), amount, options[:expires_in]) }
           end
         end
       end
@@ -120,18 +127,18 @@ module ActiveSupport
       # Clear the entire cache on all memcached servers. This method should
       # be used with care when shared cache is being used.
       def clear(options = nil)
-        rescue_error_with(nil) { @data.flush_all }
+        rescue_error_with(nil) { @data.with { |c| c.flush_all } }
       end
 
       # Get the statistics from the memcached servers.
       def stats
-        @data.stats
+        @data.with { |c| c.stats }
       end
 
       private
         # Read an entry from the cache.
         def read_entry(key, options)
-          rescue_error_with(nil) { deserialize_entry(@data.get(key, options)) }
+          rescue_error_with(nil) { deserialize_entry(@data.with { |c| c.get(key, options) }) }
         end
 
         # Write an entry to the cache.
@@ -144,7 +151,7 @@ module ActiveSupport
             expires_in += 5.minutes
           end
           rescue_error_with false do
-            @data.send(method, key, value, expires_in, options)
+            @data.with { |c| c.send(method, key, value, expires_in, options) }
           end
         end
 
@@ -152,7 +159,7 @@ module ActiveSupport
         def read_multi_entries(names, options)
           keys_to_names = Hash[names.map { |name| [normalize_key(name, options), name] }]
 
-          raw_values = @data.get_multi(keys_to_names.keys)
+          raw_values = @data.with { |c| c.get_multi(keys_to_names.keys) }
           values = {}
 
           raw_values.each do |key, value|
@@ -168,7 +175,7 @@ module ActiveSupport
 
         # Delete an entry from the cache.
         def delete_entry(key, options)
-          rescue_error_with(false) { @data.delete(key) }
+          rescue_error_with(false) { @data.with { |c| c.delete(key) } }
         end
 
         # Memcache keys are binaries. So we need to force their encoding to binary
diff --git a/activesupport/lib/active_support/cache/redis_cache_store.rb b/activesupport/lib/active_support/cache/redis_cache_store.rb
index e7f015bff5..64bc77cf22 100644
--- a/activesupport/lib/active_support/cache/redis_cache_store.rb
+++ b/activesupport/lib/active_support/cache/redis_cache_store.rb
@@ -20,6 +20,15 @@ require "active_support/core_ext/marshal"
 
 module ActiveSupport
   module Cache
+    module ConnectionPoolLike
+      def with
+        yield self
+      end
+    end
+
+    ::Redis.include(ConnectionPoolLike)
+    ::Redis::Distributed.include(ConnectionPoolLike)
+
     # Redis cache store.
     #
     # Deployment note: Take care to use a *dedicated Redis cache* rather
@@ -69,7 +78,7 @@ module ActiveSupport
 
           def write_entry(key, entry, options)
             if options[:raw] && local_cache
-              raw_entry = Entry.new(entry.value.to_s)
+              raw_entry = Entry.new(serialize_entry(entry, raw: true))
               raw_entry.expires_at = entry.expires_at
               super(key, raw_entry, options)
             else
@@ -80,7 +89,7 @@ module ActiveSupport
           def write_multi_entries(entries, options)
             if options[:raw] && local_cache
               raw_entries = entries.map do |key, entry|
-                raw_entry = Entry.new(entry.value.to_s)
+                raw_entry = Entry.new(serialize_entry(entry, raw: true))
                 raw_entry.expires_at = entry.expires_at
               end.to_h
 
@@ -149,7 +158,7 @@ module ActiveSupport
       #
       # Compression is enabled by default with a 1kB threshold, so cached
       # values larger than 1kB are automatically compressed. Disable by
-      # passing <tt>cache: false</tt> or change the threshold by passing
+      # passing <tt>compress: false</tt> or change the threshold by passing
       # <tt>compress_threshold: 4.kilobytes</tt>.
       #
       # No expiry is set on cache entries by default. Redis is expected to
@@ -172,7 +181,16 @@ module ActiveSupport
       end
 
       def redis
-        @redis ||= self.class.build_redis(**redis_options)
+        @redis ||= begin
+          pool_options = self.class.send(:retrieve_pool_options, redis_options)
+
+          if pool_options.any?
+            self.class.send(:ensure_connection_pool_added!)
+            ::ConnectionPool.new(pool_options) { self.class.build_redis(**redis_options) }
+          else
+            self.class.build_redis(**redis_options)
+          end
+        end
       end
 
       def inspect
@@ -186,7 +204,11 @@ module ActiveSupport
       # fetched values.
       def read_multi(*names)
         if mget_capable?
-          read_multi_mget(*names)
+          instrument(:read_multi, names, options) do |payload|
+            read_multi_mget(*names).tap do |results|
+              payload[:hits] = results.keys
+            end
+          end
         else
           super
         end
@@ -211,7 +233,7 @@ module ActiveSupport
         instrument :delete_matched, matcher do
           case matcher
           when String
-            redis.eval DELETE_GLOB_LUA, [], [namespace_key(matcher, options)]
+            redis.with { |c| c.eval DELETE_GLOB_LUA, [], [namespace_key(matcher, options)] }
           else
             raise ArgumentError, "Only Redis glob strings are supported: #{matcher.inspect}"
           end
@@ -228,7 +250,9 @@ module ActiveSupport
       # Failsafe: Raises errors.
       def increment(name, amount = 1, options = nil)
         instrument :increment, name, amount: amount do
-          redis.incrby normalize_key(name, options), amount
+          failsafe :increment do
+            redis.with { |c| c.incrby normalize_key(name, options), amount }
+          end
         end
       end
 
@@ -242,7 +266,9 @@ module ActiveSupport
       # Failsafe: Raises errors.
       def decrement(name, amount = 1, options = nil)
         instrument :decrement, name, amount: amount do
-          redis.decrby normalize_key(name, options), amount
+          failsafe :decrement do
+            redis.with { |c| c.decrby normalize_key(name, options), amount }
+          end
         end
       end
 
@@ -263,7 +289,7 @@ module ActiveSupport
           if namespace = merged_options(options)[namespace]
             delete_matched "*", namespace: namespace
           else
-            redis.flushdb
+            redis.with { |c| c.flushdb }
           end
         end
       end
@@ -294,7 +320,15 @@ module ActiveSupport
         # Read an entry from the cache.
         def read_entry(key, options = nil)
           failsafe :read_entry do
-            deserialize_entry redis.get(key)
+            deserialize_entry redis.with { |c| c.get(key) }
+          end
+        end
+
+        def read_multi_entries(names, _options)
+          if mget_capable?
+            read_multi_mget(*names)
+          else
+            super
           end
         end
 
@@ -303,7 +337,10 @@ module ActiveSupport
           options = merged_options(options)
 
           keys = names.map { |name| normalize_key(name, options) }
-          values = redis.mget(*keys)
+
+          values = failsafe(:read_multi_mget, returning: {}) do
+            redis.with { |c| c.mget(*keys) }
+          end
 
           names.zip(values).each_with_object({}) do |(name, value), results|
             if value
@@ -319,7 +356,7 @@ module ActiveSupport
         #
         # Requires Redis 2.6.12+ for extended SET options.
         def write_entry(key, entry, unless_exist: false, raw: false, expires_in: nil, race_condition_ttl: nil, **options)
-          value = raw ? entry.value.to_s : serialize_entry(entry)
+          serialized_entry = serialize_entry(entry, raw: raw)
 
           # If race condition TTL is in use, ensure that cache entries
           # stick around a bit longer after they would have expired
@@ -328,15 +365,15 @@ module ActiveSupport
             expires_in += 5.minutes
           end
 
-          failsafe :write_entry do
+          failsafe :write_entry, returning: false do
             if unless_exist || expires_in
               modifiers = {}
               modifiers[:nx] = unless_exist
               modifiers[:px] = (1000 * expires_in.to_f).ceil if expires_in
 
-              redis.set key, value, modifiers
+              redis.with { |c| c.set key, serialized_entry, modifiers }
             else
-              redis.set key, value
+              redis.with { |c| c.set key, serialized_entry }
             end
           end
         end
@@ -344,7 +381,7 @@ module ActiveSupport
         # Delete an entry from the cache.
         def delete_entry(key, options)
           failsafe :delete_entry, returning: false do
-            redis.del key
+            redis.with { |c| c.del key }
           end
         end
 
@@ -353,7 +390,7 @@ module ActiveSupport
           if entries.any?
             if mset_capable? && expires_in.nil?
               failsafe :write_multi_entries do
-                redis.mapped_mset(entries)
+                redis.with { |c| c.mapped_mset(serialize_entries(entries, raw: options[:raw])) }
               end
             else
               super
@@ -363,7 +400,7 @@ module ActiveSupport
 
         # Truncate keys that exceed 1kB.
         def normalize_key(key, options)
-          truncate_key super
+          truncate_key super.b
         end
 
         def truncate_key(key)
@@ -376,15 +413,25 @@ module ActiveSupport
           end
         end
 
-        def deserialize_entry(raw_value)
-          if raw_value
-            entry = Marshal.load(raw_value) rescue raw_value
+        def deserialize_entry(serialized_entry)
+          if serialized_entry
+            entry = Marshal.load(serialized_entry) rescue serialized_entry
             entry.is_a?(Entry) ? entry : Entry.new(entry)
           end
         end
 
-        def serialize_entry(entry)
-          Marshal.dump(entry)
+        def serialize_entry(entry, raw: false)
+          if raw
+            entry.value.to_s
+          else
+            Marshal.dump(entry)
+          end
+        end
+
+        def serialize_entries(entries, raw: false)
+          entries.transform_values do |entry|
+            serialize_entry entry, raw: raw
+          end
         end
 
         def failsafe(method, returning: nil)
diff --git a/activesupport/lib/active_support/cache/strategy/local_cache.rb b/activesupport/lib/active_support/cache/strategy/local_cache.rb
index aaa9638fa8..e17308f83e 100644
--- a/activesupport/lib/active_support/cache/strategy/local_cache.rb
+++ b/activesupport/lib/active_support/cache/strategy/local_cache.rb
@@ -54,6 +54,10 @@ module ActiveSupport
             @data[key]
           end
 
+          def read_multi_entries(keys, options)
+            Hash[keys.map { |name| [name, read_entry(name, options)] }.keep_if { |_name, value| value }]
+          end
+
           def write_entry(key, value, options)
             @data[key] = value
             true
@@ -116,6 +120,19 @@ module ActiveSupport
             end
           end
 
+          def read_multi_entries(keys, options)
+            return super unless local_cache
+
+            local_entries = local_cache.read_multi_entries(keys, options)
+            missed_keys = keys - local_entries.keys
+
+            if missed_keys.any?
+              local_entries.merge!(super(missed_keys, options))
+            else
+              local_entries
+            end
+          end
+
           def write_entry(key, entry, options)
             if options[:unless_exist]
               local_cache.delete_entry(key, options) if local_cache
diff --git a/activesupport/lib/active_support/core_ext/class/attribute.rb b/activesupport/lib/active_support/core_ext/class/attribute.rb
index 7928efb871..fa33ff945f 100644
--- a/activesupport/lib/active_support/core_ext/class/attribute.rb
+++ b/activesupport/lib/active_support/core_ext/class/attribute.rb
@@ -98,7 +98,7 @@ class Class
       singleton_class.silence_redefinition_of_method("#{name}?")
       define_singleton_method("#{name}?") { !!public_send(name) } if instance_predicate
 
-      ivar = "@#{name}"
+      ivar = "@#{name}".to_sym
 
       singleton_class.silence_redefinition_of_method("#{name}=")
       define_singleton_method("#{name}=") do |val|
diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb
index e19aeaa983..325581a60a 100644
--- a/activesupport/lib/active_support/core_ext/hash.rb
+++ b/activesupport/lib/active_support/core_ext/hash.rb
@@ -8,4 +8,3 @@ require "active_support/core_ext/hash/indifferent_access"
 require "active_support/core_ext/hash/keys"
 require "active_support/core_ext/hash/reverse_merge"
 require "active_support/core_ext/hash/slice"
-require "active_support/core_ext/hash/transform_values"
diff --git a/activesupport/lib/active_support/core_ext/hash/conversions.rb b/activesupport/lib/active_support/core_ext/hash/conversions.rb
index 11d28d12a1..5b48254646 100644
--- a/activesupport/lib/active_support/core_ext/hash/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/hash/conversions.rb
@@ -165,7 +165,7 @@ module ActiveSupport
           Hash[params.map { |k, v| [k.to_s.tr("-", "_"), normalize_keys(v)] } ]
         when Array
           params.map { |v| normalize_keys(v) }
-          else
+        else
           params
         end
       end
@@ -178,7 +178,7 @@ module ActiveSupport
           process_array(value)
         when String
           value
-          else
+        else
           raise "can't typecast #{value.class.name} - #{value.inspect}"
         end
       end
diff --git a/activesupport/lib/active_support/core_ext/hash/transform_values.rb b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
index 4b19c9fc1f..fc15130c9e 100644
--- a/activesupport/lib/active_support/core_ext/hash/transform_values.rb
+++ b/activesupport/lib/active_support/core_ext/hash/transform_values.rb
@@ -1,32 +1,5 @@
 # frozen_string_literal: true
 
-class Hash
-  # Returns a new hash with the results of running +block+ once for every value.
-  # The keys are unchanged.
-  #
-  #   { a: 1, b: 2, c: 3 }.transform_values { |x| x * 2 } # => { a: 2, b: 4, c: 6 }
-  #
-  # If you do not provide a +block+, it will return an Enumerator
-  # for chaining with other methods:
-  #
-  #   { a: 1, b: 2 }.transform_values.with_index { |v, i| [v, i].join.to_i } # => { a: 10, b: 21 }
-  def transform_values
-    return enum_for(:transform_values) { size } unless block_given?
-    return {} if empty?
-    result = self.class.new
-    each do |key, value|
-      result[key] = yield(value)
-    end
-    result
-  end unless method_defined? :transform_values
+require "active_support/deprecation"
 
-  # Destructively converts all values using the +block+ operations.
-  # Same as +transform_values+ but modifies +self+.
-  def transform_values!
-    return enum_for(:transform_values!) { size } unless block_given?
-    each do |key, value|
-      self[key] = yield(value)
-    end
-  end unless method_defined? :transform_values!
-  # TODO: Remove this file when supporting only Ruby 2.4+.
-end
+ActiveSupport::Deprecation.warn "Ruby 2.4+ (required by Rails 6) provides Hash#transform_values natively, so requiring active_support/core_ext/hash/transform_values is no longer necessary. Requiring it will raise LoadError in Rails 6.1."
diff --git a/activesupport/lib/active_support/core_ext/module/redefine_method.rb b/activesupport/lib/active_support/core_ext/module/redefine_method.rb
index a0a6622ca4..5bd8e6e973 100644
--- a/activesupport/lib/active_support/core_ext/module/redefine_method.rb
+++ b/activesupport/lib/active_support/core_ext/module/redefine_method.rb
@@ -1,23 +1,14 @@
 # frozen_string_literal: true
 
 class Module
-  if RUBY_VERSION >= "2.3"
-    # Marks the named method as intended to be redefined, if it exists.
-    # Suppresses the Ruby method redefinition warning. Prefer
-    # #redefine_method where possible.
-    def silence_redefinition_of_method(method)
-      if method_defined?(method) || private_method_defined?(method)
-        # This suppresses the "method redefined" warning; the self-alias
-        # looks odd, but means we don't need to generate a unique name
-        alias_method method, method
-      end
-    end
-  else
-    def silence_redefinition_of_method(method)
-      if method_defined?(method) || private_method_defined?(method)
-        alias_method :__rails_redefine, method
-        remove_method :__rails_redefine
-      end
+  # Marks the named method as intended to be redefined, if it exists.
+  # Suppresses the Ruby method redefinition warning. Prefer
+  # #redefine_method where possible.
+  def silence_redefinition_of_method(method)
+    if method_defined?(method) || private_method_defined?(method)
+      # This suppresses the "method redefined" warning; the self-alias
+      # looks odd, but means we don't need to generate a unique name
+      alias_method method, method
     end
   end
 
diff --git a/activesupport/lib/active_support/core_ext/numeric/conversions.rb b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
index f6c2713986..7fcd0d0311 100644
--- a/activesupport/lib/active_support/core_ext/numeric/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/numeric/conversions.rb
@@ -129,12 +129,6 @@ module ActiveSupport::NumericWithFormat
   end
 end
 
-# Ruby 2.4+ unifies Fixnum & Bignum into Integer.
-if 0.class == Integer
-  Integer.prepend ActiveSupport::NumericWithFormat
-else
-  Fixnum.prepend ActiveSupport::NumericWithFormat
-  Bignum.prepend ActiveSupport::NumericWithFormat
-end
+Integer.prepend ActiveSupport::NumericWithFormat
 Float.prepend ActiveSupport::NumericWithFormat
 BigDecimal.prepend ActiveSupport::NumericWithFormat
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb
index 9bb99087bc..c78ee6bbfc 100644
--- a/activesupport/lib/active_support/core_ext/object/duplicable.rb
+++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb
@@ -75,8 +75,11 @@ end
 
 class Symbol
   begin
-    :symbol.dup # Ruby 2.4.x.
-    "symbol_from_string".to_sym.dup # Some symbols can't `dup` in Ruby 2.4.0.
+    :symbol.dup
+
+    # Some symbols couldn't be duped in Ruby 2.4.0 only, due to a bug.
+    # This feature check catches any regression.
+    "symbol_from_string".to_sym.dup
   rescue TypeError
 
     # Symbols are not duplicable:
diff --git a/activesupport/lib/active_support/core_ext/regexp.rb b/activesupport/lib/active_support/core_ext/regexp.rb
index efbd708aee..d92943c7ae 100644
--- a/activesupport/lib/active_support/core_ext/regexp.rb
+++ b/activesupport/lib/active_support/core_ext/regexp.rb
@@ -4,8 +4,4 @@ class Regexp #:nodoc:
   def multiline?
     options & MULTILINE == MULTILINE
   end
-
-  def match?(string, pos = 0)
-    !!match(string, pos)
-  end unless //.respond_to?(:match?)
 end
diff --git a/activesupport/lib/active_support/core_ext/string/filters.rb b/activesupport/lib/active_support/core_ext/string/filters.rb
index 66e721eea3..df0e79afa8 100644
--- a/activesupport/lib/active_support/core_ext/string/filters.rb
+++ b/activesupport/lib/active_support/core_ext/string/filters.rb
@@ -78,6 +78,47 @@ class String
     "#{self[0, stop]}#{omission}"
   end
 
+  # Truncates +text+ to at most <tt>bytesize</tt> bytes in length without
+  # breaking string encoding by splitting multibyte characters or breaking
+  # grapheme clusters ("perceptual characters") by truncating at combining
+  # characters.
+  #
+  #   >> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".size
+  #   => 20
+  #   >> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".bytesize
+  #   => 80
+  #   >> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".truncate_bytes(20)
+  #   => "🔪🔪🔪🔪…"
+  #
+  # The truncated text ends with the <tt>:omission</tt> string, defaulting
+  # to "…", for a total length not exceeding <tt>bytesize</tt>.
+  def truncate_bytes(truncate_at, omission: "…")
+    omission ||= ""
+
+    case
+    when bytesize <= truncate_at
+      dup
+    when omission.bytesize > truncate_at
+      raise ArgumentError, "Omission #{omission.inspect} is #{omission.bytesize}, larger than the truncation length of #{truncate_at} bytes"
+    when omission.bytesize == truncate_at
+      omission.dup
+    else
+      self.class.new.tap do |cut|
+        cut_at = truncate_at - omission.bytesize
+
+        scan(/\X/) do |grapheme|
+          if cut.bytesize + grapheme.bytesize <= cut_at
+            cut << grapheme
+          else
+            break
+          end
+        end
+
+        cut << omission
+      end
+    end
+  end
+
   # Truncates a given +text+ after a given number of words (<tt>words_count</tt>):
   #
   #   'Once upon a time in a world far far away'.truncate_words(4)
diff --git a/activesupport/lib/active_support/core_ext/string/multibyte.rb b/activesupport/lib/active_support/core_ext/string/multibyte.rb
index 07c0d16398..6cceb46507 100644
--- a/activesupport/lib/active_support/core_ext/string/multibyte.rb
+++ b/activesupport/lib/active_support/core_ext/string/multibyte.rb
@@ -11,12 +11,13 @@ class String
   # encapsulates the original string. A Unicode safe version of all the String methods are defined on this proxy
   # class. If the proxy class doesn't respond to a certain method, it's forwarded to the encapsulated string.
   #
-  #   >> "lj".upcase
-  #   => "lj"
   #   >> "lj".mb_chars.upcase.to_s
   #   => "LJ"
   #
-  # NOTE: An above example is useful for pre Ruby 2.4. Ruby 2.4 supports Unicode case mappings.
+  # NOTE: Ruby 2.4 and later support native Unicode case mappings:
+  #
+  #   >> "lj".upcase
+  #   => "LJ"
   #
   # == Method chaining
   #
diff --git a/activesupport/lib/active_support/core_ext/string/strip.rb b/activesupport/lib/active_support/core_ext/string/strip.rb
index cc26274e4a..6f9834bb16 100644
--- a/activesupport/lib/active_support/core_ext/string/strip.rb
+++ b/activesupport/lib/active_support/core_ext/string/strip.rb
@@ -20,6 +20,8 @@ class String
   # Technically, it looks for the least indented non-empty line
   # in the whole string, and removes that amount of leading whitespace.
   def strip_heredoc
-    gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, "".freeze)
+    gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, "".freeze).tap do |stripped|
+      stripped.freeze if frozen?
+    end
   end
 end
diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index 82c10b3079..0f59558bb5 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -447,6 +447,7 @@ module ActiveSupport #:nodoc:
       mod = Module.new
       into.const_set const_name, mod
       autoloaded_constants << qualified_name unless autoload_once_paths.include?(base_path)
+      autoloaded_constants.uniq!
       mod
     end
 
@@ -670,7 +671,7 @@ module ActiveSupport #:nodoc:
       when Module
         desc.name ||
           raise(ArgumentError, "Anonymous modules have no name to be referenced by")
-        else raise TypeError, "Not a valid constant descriptor: #{desc.inspect}"
+      else raise TypeError, "Not a valid constant descriptor: #{desc.inspect}"
       end
     end
 
diff --git a/activesupport/lib/active_support/deprecation.rb b/activesupport/lib/active_support/deprecation.rb
index a1ad2ca465..7271ab565b 100644
--- a/activesupport/lib/active_support/deprecation.rb
+++ b/activesupport/lib/active_support/deprecation.rb
@@ -35,7 +35,7 @@ module ActiveSupport
     # and the second is a library name.
     #
     #   ActiveSupport::Deprecation.new('2.0', 'MyLibrary')
-    def initialize(deprecation_horizon = "6.0", gem_name = "Rails")
+    def initialize(deprecation_horizon = "6.1", gem_name = "Rails")
       self.gem_name = gem_name
       self.deprecation_horizon = deprecation_horizon
       # By default, warnings are not silenced and debugging is off.
diff --git a/activesupport/lib/active_support/deprecation/behaviors.rb b/activesupport/lib/active_support/deprecation/behaviors.rb
index 581db5f449..66d6f3225a 100644
--- a/activesupport/lib/active_support/deprecation/behaviors.rb
+++ b/activesupport/lib/active_support/deprecation/behaviors.rb
@@ -85,7 +85,7 @@ module ActiveSupport
       #   ActiveSupport::Deprecation.behavior = :stderr
       #   ActiveSupport::Deprecation.behavior = [:stderr, :log]
       #   ActiveSupport::Deprecation.behavior = MyCustomHandler
-      #   ActiveSupport::Deprecation.behavior = ->(message, callstack) {
+      #   ActiveSupport::Deprecation.behavior = ->(message, callstack, deprecation_horizon, gem_name) {
       #     # custom stuff
       #   }
       def behavior=(behavior)
diff --git a/activesupport/lib/active_support/deprecation/reporting.rb b/activesupport/lib/active_support/deprecation/reporting.rb
index 242e21b782..2c004f4c9e 100644
--- a/activesupport/lib/active_support/deprecation/reporting.rb
+++ b/activesupport/lib/active_support/deprecation/reporting.rb
@@ -61,7 +61,7 @@ module ActiveSupport
           case message
           when Symbol then "#{warning} (use #{message} instead)"
           when String then "#{warning} (#{message})"
-            else warning
+          else warning
           end
         end
 
diff --git a/activesupport/lib/active_support/duration.rb b/activesupport/lib/active_support/duration.rb
index fe1058762b..88897f811e 100644
--- a/activesupport/lib/active_support/duration.rb
+++ b/activesupport/lib/active_support/duration.rb
@@ -383,6 +383,14 @@ module ActiveSupport
       to_i
     end
 
+    def init_with(coder) #:nodoc:
+      initialize(coder["value"], coder["parts"])
+    end
+
+    def encode_with(coder) #:nodoc:
+      coder.map = { "value" => @value, "parts" => @parts }
+    end
+
     # Build ISO 8601 Duration string for this duration.
     # The +precision+ parameter can be used to limit seconds' precision of duration.
     def iso8601(precision: nil)
diff --git a/activesupport/lib/active_support/duration/iso8601_serializer.rb b/activesupport/lib/active_support/duration/iso8601_serializer.rb
index bb177ae5b7..84ae29c1ec 100644
--- a/activesupport/lib/active_support/duration/iso8601_serializer.rb
+++ b/activesupport/lib/active_support/duration/iso8601_serializer.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/object/blank"
-require "active_support/core_ext/hash/transform_values"
 
 module ActiveSupport
   class Duration
diff --git a/activesupport/lib/active_support/gem_version.rb b/activesupport/lib/active_support/gem_version.rb
index 1e09adbb52..c951ad16a3 100644
--- a/activesupport/lib/active_support/gem_version.rb
+++ b/activesupport/lib/active_support/gem_version.rb
@@ -7,10 +7,10 @@ module ActiveSupport
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 2e2ed8a25d..e4afc8af93 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -177,20 +177,18 @@ module ActiveSupport
       super(convert_key(key), *extras)
     end
 
-    if Hash.new.respond_to?(:dig)
-      # Same as <tt>Hash#dig</tt> where the key passed as argument can be
-      # either a string or a symbol:
-      #
-      #   counters = ActiveSupport::HashWithIndifferentAccess.new
-      #   counters[:foo] = { bar: 1 }
-      #
-      #   counters.dig('foo', 'bar')     # => 1
-      #   counters.dig(:foo, :bar)       # => 1
-      #   counters.dig(:zoo)             # => nil
-      def dig(*args)
-        args[0] = convert_key(args[0]) if args.size > 0
-        super(*args)
-      end
+    # Same as <tt>Hash#dig</tt> where the key passed as argument can be
+    # either a string or a symbol:
+    #
+    #   counters = ActiveSupport::HashWithIndifferentAccess.new
+    #   counters[:foo] = { bar: 1 }
+    #
+    #   counters.dig('foo', 'bar')     # => 1
+    #   counters.dig(:foo, :bar)       # => 1
+    #   counters.dig(:zoo)             # => nil
+    def dig(*args)
+      args[0] = convert_key(args[0]) if args.size > 0
+      super(*args)
     end
 
     # Same as <tt>Hash#default</tt> where the key passed as argument can be
@@ -228,7 +226,7 @@ module ActiveSupport
     #   hash.fetch_values('a', 'c') # => KeyError: key not found: "c"
     def fetch_values(*indices, &block)
       indices.collect { |key| fetch(key, &block) }
-    end if Hash.method_defined?(:fetch_values)
+    end
 
     # Returns a shallow copy of the hash.
     #
@@ -311,6 +309,14 @@ module ActiveSupport
       dup.tap { |hash| hash.transform_keys!(*args, &block) }
     end
 
+    def transform_keys!
+      return enum_for(:transform_keys!) { size } unless block_given?
+      keys.each do |key|
+        self[yield(key)] = delete(key)
+      end
+      self
+    end
+
     def slice(*keys)
       keys.map! { |key| convert_key(key) }
       self.class.new(super)
diff --git a/activesupport/lib/active_support/inflector/inflections.rb b/activesupport/lib/active_support/inflector/inflections.rb
index 0450a4be4c..7e5dff1d6d 100644
--- a/activesupport/lib/active_support/inflector/inflections.rb
+++ b/activesupport/lib/active_support/inflector/inflections.rb
@@ -227,7 +227,7 @@ module ActiveSupport
         case scope
         when :all
           @plurals, @singulars, @uncountables, @humans = [], [], Uncountables.new, []
-          else
+        else
           instance_variable_set "@#{scope}", []
         end
       end
diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index 60eeaa77cb..7e782e2a93 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -350,7 +350,7 @@ module ActiveSupport
         when 1; "st"
         when 2; "nd"
         when 3; "rd"
-          else    "th"
+        else    "th"
         end
       end
     end
diff --git a/activesupport/lib/active_support/multibyte/unicode.rb b/activesupport/lib/active_support/multibyte/unicode.rb
index a64223c0e0..4f0e1165ef 100644
--- a/activesupport/lib/active_support/multibyte/unicode.rb
+++ b/activesupport/lib/active_support/multibyte/unicode.rb
@@ -11,7 +11,7 @@ module ActiveSupport
       NORMALIZATION_FORMS = [:c, :kc, :d, :kd]
 
       # The Unicode version that is supported by the implementation
-      UNICODE_VERSION = "9.0.0"
+      UNICODE_VERSION = RbConfig::CONFIG["UNICODE_VERSION"]
 
       # The default normalization used for operations that require
       # normalization. It can be set to any of the normalizations
@@ -21,96 +21,13 @@ module ActiveSupport
       attr_accessor :default_normalization_form
       @default_normalization_form = :kc
 
-      # Hangul character boundaries and properties
-      HANGUL_SBASE = 0xAC00
-      HANGUL_LBASE = 0x1100
-      HANGUL_VBASE = 0x1161
-      HANGUL_TBASE = 0x11A7
-      HANGUL_LCOUNT = 19
-      HANGUL_VCOUNT = 21
-      HANGUL_TCOUNT = 28
-      HANGUL_NCOUNT = HANGUL_VCOUNT * HANGUL_TCOUNT
-      HANGUL_SCOUNT = 11172
-      HANGUL_SLAST = HANGUL_SBASE + HANGUL_SCOUNT
-
-      # Detect whether the codepoint is in a certain character class. Returns
-      # +true+ when it's in the specified character class and +false+ otherwise.
-      # Valid character classes are: <tt>:cr</tt>, <tt>:lf</tt>, <tt>:l</tt>,
-      # <tt>:v</tt>, <tt>:lv</tt>, <tt>:lvt</tt> and <tt>:t</tt>.
-      #
-      # Primarily used by the grapheme cluster support.
-      def in_char_class?(codepoint, classes)
-        classes.detect { |c| database.boundary[c] === codepoint } ? true : false
-      end
-
       # Unpack the string at grapheme boundaries. Returns a list of character
       # lists.
       #
       #   Unicode.unpack_graphemes('क्षि') # => [[2325, 2381], [2359], [2367]]
       #   Unicode.unpack_graphemes('Café') # => [[67], [97], [102], [233]]
       def unpack_graphemes(string)
-        codepoints = string.codepoints.to_a
-        unpacked = []
-        pos = 0
-        marker = 0
-        eoc = codepoints.length
-        while (pos < eoc)
-          pos += 1
-          previous = codepoints[pos - 1]
-          current = codepoints[pos]
-
-          # See http://unicode.org/reports/tr29/#Grapheme_Cluster_Boundary_Rules
-          should_break =
-            if pos == eoc
-              true
-            # GB3. CR X LF
-            elsif previous == database.boundary[:cr] && current == database.boundary[:lf]
-              false
-            # GB4. (Control|CR|LF) ÷
-            elsif previous && in_char_class?(previous, [:control, :cr, :lf])
-              true
-            # GB5. ÷ (Control|CR|LF)
-            elsif in_char_class?(current, [:control, :cr, :lf])
-              true
-            # GB6. L X (L|V|LV|LVT)
-            elsif database.boundary[:l] === previous && in_char_class?(current, [:l, :v, :lv, :lvt])
-              false
-            # GB7. (LV|V) X (V|T)
-            elsif in_char_class?(previous, [:lv, :v]) && in_char_class?(current, [:v, :t])
-              false
-            # GB8. (LVT|T) X (T)
-            elsif in_char_class?(previous, [:lvt, :t]) && database.boundary[:t] === current
-              false
-            # GB9. X (Extend | ZWJ)
-            elsif in_char_class?(current, [:extend, :zwj])
-              false
-            # GB9a. X SpacingMark
-            elsif database.boundary[:spacingmark] === current
-              false
-            # GB9b. Prepend X
-            elsif database.boundary[:prepend] === previous
-              false
-            # GB10. (E_Base | EBG) Extend* X E_Modifier
-            elsif (marker...pos).any? { |i| in_char_class?(codepoints[i], [:e_base, :e_base_gaz]) && codepoints[i + 1...pos].all? { |c| database.boundary[:extend] === c } } && database.boundary[:e_modifier] === current
-              false
-            # GB11. ZWJ X (Glue_After_Zwj | EBG)
-            elsif database.boundary[:zwj] === previous && in_char_class?(current, [:glue_after_zwj, :e_base_gaz])
-              false
-            # GB12. ^ (RI RI)* RI X RI
-            # GB13. [^RI] (RI RI)* RI X RI
-            elsif codepoints[marker..pos].all? { |c| database.boundary[:regional_indicator] === c } && codepoints[marker..pos].count { |c| database.boundary[:regional_indicator] === c }.even?
-              false
-            # GB999. Any ÷ Any
-            else
-              true
-            end
-
-          if should_break
-            unpacked << codepoints[marker..pos - 1]
-            marker = pos
-          end
-        end
-        unpacked
+        string.scan(/\X/).map(&:codepoints)
       end
 
       # Reverse operation of unpack_graphemes.
@@ -120,100 +37,18 @@ module ActiveSupport
         unpacked.flatten.pack("U*")
       end
 
-      # Re-order codepoints so the string becomes canonical.
-      def reorder_characters(codepoints)
-        length = codepoints.length - 1
-        pos = 0
-        while pos < length do
-          cp1, cp2 = database.codepoints[codepoints[pos]], database.codepoints[codepoints[pos + 1]]
-          if (cp1.combining_class > cp2.combining_class) && (cp2.combining_class > 0)
-            codepoints[pos..pos + 1] = cp2.code, cp1.code
-            pos += (pos > 0 ? -1 : 1)
-          else
-            pos += 1
-          end
-        end
-        codepoints
-      end
-
       # Decompose composed characters to the decomposed form.
       def decompose(type, codepoints)
-        codepoints.inject([]) do |decomposed, cp|
-          # if it's a hangul syllable starter character
-          if HANGUL_SBASE <= cp && cp < HANGUL_SLAST
-            sindex = cp - HANGUL_SBASE
-            ncp = [] # new codepoints
-            ncp << HANGUL_LBASE + sindex / HANGUL_NCOUNT
-            ncp << HANGUL_VBASE + (sindex % HANGUL_NCOUNT) / HANGUL_TCOUNT
-            tindex = sindex % HANGUL_TCOUNT
-            ncp << (HANGUL_TBASE + tindex) unless tindex == 0
-            decomposed.concat ncp
-          # if the codepoint is decomposable in with the current decomposition type
-          elsif (ncp = database.codepoints[cp].decomp_mapping) && (!database.codepoints[cp].decomp_type || type == :compatibility)
-            decomposed.concat decompose(type, ncp.dup)
-          else
-            decomposed << cp
-          end
+        if type == :compatibility
+          codepoints.pack("U*").unicode_normalize(:nfkd).codepoints
+        else
+          codepoints.pack("U*").unicode_normalize(:nfd).codepoints
         end
       end
 
       # Compose decomposed characters to the composed form.
       def compose(codepoints)
-        pos = 0
-        eoa = codepoints.length - 1
-        starter_pos = 0
-        starter_char = codepoints[0]
-        previous_combining_class = -1
-        while pos < eoa
-          pos += 1
-          lindex = starter_char - HANGUL_LBASE
-          # -- Hangul
-          if 0 <= lindex && lindex < HANGUL_LCOUNT
-            vindex = codepoints[starter_pos + 1] - HANGUL_VBASE rescue vindex = -1
-            if 0 <= vindex && vindex < HANGUL_VCOUNT
-              tindex = codepoints[starter_pos + 2] - HANGUL_TBASE rescue tindex = -1
-              if 0 <= tindex && tindex < HANGUL_TCOUNT
-                j = starter_pos + 2
-                eoa -= 2
-              else
-                tindex = 0
-                j = starter_pos + 1
-                eoa -= 1
-              end
-              codepoints[starter_pos..j] = (lindex * HANGUL_VCOUNT + vindex) * HANGUL_TCOUNT + tindex + HANGUL_SBASE
-            end
-            starter_pos += 1
-            starter_char = codepoints[starter_pos]
-          # -- Other characters
-          else
-            current_char = codepoints[pos]
-            current = database.codepoints[current_char]
-            if current.combining_class > previous_combining_class
-              if ref = database.composition_map[starter_char]
-                composition = ref[current_char]
-              else
-                composition = nil
-              end
-              unless composition.nil?
-                codepoints[starter_pos] = composition
-                starter_char = composition
-                codepoints.delete_at pos
-                eoa -= 1
-                pos -= 1
-                previous_combining_class = -1
-              else
-                previous_combining_class = current.combining_class
-              end
-            else
-              previous_combining_class = current.combining_class
-            end
-            if current.combining_class == 0
-              starter_pos = pos
-              starter_char = codepoints[pos]
-            end
-          end
-        end
-        codepoints
+        codepoints.pack("U*").unicode_normalize(:nfc).codepoints
       end
 
       # Rubinius' String#scrub, however, doesn't support ASCII-incompatible chars.
@@ -266,129 +101,37 @@ module ActiveSupport
       def normalize(string, form = nil)
         form ||= @default_normalization_form
         # See http://www.unicode.org/reports/tr15, Table 1
-        codepoints = string.codepoints.to_a
         case form
         when :d
-          reorder_characters(decompose(:canonical, codepoints))
+          string.unicode_normalize(:nfd)
         when :c
-          compose(reorder_characters(decompose(:canonical, codepoints)))
+          string.unicode_normalize(:nfc)
         when :kd
-          reorder_characters(decompose(:compatibility, codepoints))
+          string.unicode_normalize(:nfkd)
         when :kc
-          compose(reorder_characters(decompose(:compatibility, codepoints)))
-          else
+          string.unicode_normalize(:nfkc)
+        else
           raise ArgumentError, "#{form} is not a valid normalization variant", caller
-        end.pack("U*".freeze)
+        end
       end
 
       def downcase(string)
-        apply_mapping string, :lowercase_mapping
+        string.downcase
       end
 
       def upcase(string)
-        apply_mapping string, :uppercase_mapping
+        string.upcase
       end
 
       def swapcase(string)
-        apply_mapping string, :swapcase_mapping
-      end
-
-      # Holds data about a codepoint in the Unicode database.
-      class Codepoint
-        attr_accessor :code, :combining_class, :decomp_type, :decomp_mapping, :uppercase_mapping, :lowercase_mapping
-
-        # Initializing Codepoint object with default values
-        def initialize
-          @combining_class = 0
-          @uppercase_mapping = 0
-          @lowercase_mapping = 0
-        end
-
-        def swapcase_mapping
-          uppercase_mapping > 0 ? uppercase_mapping : lowercase_mapping
-        end
-      end
-
-      # Holds static data from the Unicode database.
-      class UnicodeDatabase
-        ATTRIBUTES = :codepoints, :composition_exclusion, :composition_map, :boundary, :cp1252
-
-        attr_writer(*ATTRIBUTES)
-
-        def initialize
-          @codepoints = Hash.new(Codepoint.new)
-          @composition_exclusion = []
-          @composition_map = {}
-          @boundary = {}
-          @cp1252 = {}
-        end
-
-        # Lazy load the Unicode database so it's only loaded when it's actually used
-        ATTRIBUTES.each do |attr_name|
-          class_eval(<<-EOS, __FILE__, __LINE__ + 1)
-            def #{attr_name}     # def codepoints
-              load               #   load
-              @#{attr_name}      #   @codepoints
-            end                  # end
-          EOS
-        end
-
-        # Loads the Unicode database and returns all the internal objects of
-        # UnicodeDatabase.
-        def load
-          begin
-            @codepoints, @composition_exclusion, @composition_map, @boundary, @cp1252 = File.open(self.class.filename, "rb") { |f| Marshal.load f.read }
-          rescue => e
-            raise IOError.new("Couldn't load the Unicode tables for UTF8Handler (#{e.message}), ActiveSupport::Multibyte is unusable")
-          end
-
-          # Redefine the === method so we can write shorter rules for grapheme cluster breaks
-          @boundary.each_key do |k|
-            @boundary[k].instance_eval do
-              def ===(other)
-                detect { |i| i === other } ? true : false
-              end
-            end if @boundary[k].kind_of?(Array)
-          end
-
-          # define attr_reader methods for the instance variables
-          class << self
-            attr_reader(*ATTRIBUTES)
-          end
-        end
-
-        # Returns the directory in which the data files are stored.
-        def self.dirname
-          File.expand_path("../values", __dir__)
-        end
-
-        # Returns the filename for the data file for this version.
-        def self.filename
-          File.expand_path File.join(dirname, "unicode_tables.dat")
-        end
+        string.swapcase
       end
 
       private
 
-        def apply_mapping(string, mapping)
-          database.codepoints
-          string.each_codepoint.map do |codepoint|
-            cp = database.codepoints[codepoint]
-            if cp && (ncp = cp.send(mapping)) && ncp > 0
-              ncp
-            else
-              codepoint
-            end
-          end.pack("U*")
-        end
-
         def recode_windows1252_chars(string)
           string.encode(Encoding::UTF_8, Encoding::Windows_1252, invalid: :replace, undef: :replace)
         end
-
-        def database
-          @database ||= UnicodeDatabase.new
-        end
     end
   end
 end
diff --git a/activesupport/lib/active_support/rails.rb b/activesupport/lib/active_support/rails.rb
index 5c34a0abb3..8b727a69ec 100644
--- a/activesupport/lib/active_support/rails.rb
+++ b/activesupport/lib/active_support/rails.rb
@@ -27,9 +27,3 @@ require "active_support/core_ext/module/delegation"
 
 # Defines ActiveSupport::Deprecation.
 require "active_support/deprecation"
-
-# Defines Regexp#match?.
-#
-# This should be removed when Rails needs Ruby 2.4 or later, and the require
-# added where other Regexp extensions are being used (easy to grep).
-require "active_support/core_ext/regexp"
diff --git a/activesupport/lib/active_support/subscriber.rb b/activesupport/lib/active_support/subscriber.rb
index d6dd5474d0..8ad39f7a05 100644
--- a/activesupport/lib/active_support/subscriber.rb
+++ b/activesupport/lib/active_support/subscriber.rb
@@ -54,25 +54,20 @@ module ActiveSupport
         @@subscribers ||= []
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-      attr_reader :subscriber, :notifier, :namespace
-
       private
+        attr_reader :subscriber, :notifier, :namespace
 
-      def add_event_subscriber(event) # :doc:
-        return if %w{ start finish }.include?(event.to_s)
+        def add_event_subscriber(event) # :doc:
+          return if %w{ start finish }.include?(event.to_s)
 
-        pattern = "#{event}.#{namespace}"
+          pattern = "#{event}.#{namespace}"
 
-        # Don't add multiple subscribers (eg. if methods are redefined).
-        return if subscriber.patterns.include?(pattern)
+          # Don't add multiple subscribers (eg. if methods are redefined).
+          return if subscriber.patterns.include?(pattern)
 
-        subscriber.patterns << pattern
-        notifier.subscribe(pattern, subscriber)
-      end
+          subscriber.patterns << pattern
+          notifier.subscribe(pattern, subscriber)
+        end
     end
 
     attr_reader :patterns # :nodoc:
diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index d1f7e6ea09..a698b4e61e 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -11,6 +11,7 @@ require "active_support/testing/isolation"
 require "active_support/testing/constant_lookup"
 require "active_support/testing/time_helpers"
 require "active_support/testing/file_fixtures"
+require "active_support/testing/parallelization"
 
 module ActiveSupport
   class TestCase < ::Minitest::Test
@@ -39,6 +40,91 @@ module ActiveSupport
       def test_order
         ActiveSupport.test_order ||= :random
       end
+
+      # Parallelizes the test suite.
+      #
+      # Takes a `workers` argument that controls how many times the process
+      # is forked. For each process a new database will be created suffixed
+      # with the worker number.
+      #
+      #   test-database-0
+      #   test-database-1
+      #
+      # If `ENV["PARALLEL_WORKERS"]` is set the workers argument will be ignored
+      # and the environment variable will be used instead. This is useful for CI
+      # environments, or other environments where you may need more workers than
+      # you do for local testing.
+      #
+      # If the number of workers is set to `1` or fewer, the tests will not be
+      # parallelized.
+      #
+      # The default parallelization method is to fork processes. If you'd like to
+      # use threads instead you can pass `with: :threads` to the `parallelize`
+      # method. Note the threaded parallelization does not create multiple
+      # database and will not work with system tests at this time.
+      #
+      #   parallelize(workers: 2, with: :threads)
+      #
+      # The threaded parallelization uses Minitest's parallel executor directly.
+      # The processes parallelization uses a Ruby Drb server.
+      def parallelize(workers: 2, with: :processes)
+        workers = ENV["PARALLEL_WORKERS"].to_i if ENV["PARALLEL_WORKERS"]
+
+        return if workers <= 1
+
+        executor = case with
+                   when :processes
+                     Testing::Parallelization.new(workers)
+                   when :threads
+                     Minitest::Parallel::Executor.new(workers)
+                   else
+                     raise ArgumentError, "#{with} is not a supported parallelization executor."
+        end
+
+        self.lock_threads = false if defined?(self.lock_threads) && with == :threads
+
+        Minitest.parallel_executor = executor
+
+        parallelize_me!
+      end
+
+      # Set up hook for parallel testing. This can be used if you have multiple
+      # databases or any behavior that needs to be run after the process is forked
+      # but before the tests run.
+      #
+      # Note: this feature is not available with the threaded parallelization.
+      #
+      # In your +test_helper.rb+ add the following:
+      #
+      #   class ActiveSupport::TestCase
+      #     parallelize_setup do
+      #       # create databases
+      #     end
+      #   end
+      def parallelize_setup(&block)
+        ActiveSupport::Testing::Parallelization.after_fork_hook do |worker|
+          yield worker
+        end
+      end
+
+      # Clean up hook for parallel testing. This can be used to drop databases
+      # if your app uses multiple write/read databases or other clean up before
+      # the tests finish. This runs before the forked process is closed.
+      #
+      # Note: this feature is not available with the threaded parallelization.
+      #
+      # In your +test_helper.rb+ add the following:
+      #
+      #   class ActiveSupport::TestCase
+      #     parallelize_teardown do
+      #       # drop databases
+      #     end
+      #   end
+      def parallelize_teardown(&block)
+        ActiveSupport::Testing::Parallelization.run_cleanup_hook do |worker|
+          yield worker
+        end
+      end
     end
 
     alias_method :method_name, :name
diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index 6f69c48674..a891ff616d 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -58,6 +58,12 @@ module ActiveSupport
       #     post :create, params: { article: {...} }
       #   end
       #
+      # A hash of expressions/numeric differences can also be passed in and evaluated.
+      #
+      #   assert_difference ->{ Article.count } => 1, ->{ Notification.count } => 2 do
+      #     post :create, params: { article: {...} }
+      #   end
+      #
       # A lambda or a list of lambdas can be passed in and evaluated:
       #
       #   assert_difference ->{ Article.count }, 2 do
@@ -73,20 +79,28 @@ module ActiveSupport
       #   assert_difference 'Article.count', -1, 'An Article should be destroyed' do
       #     post :delete, params: { id: ... }
       #   end
-      def assert_difference(expression, difference = 1, message = nil, &block)
-        expressions = Array(expression)
-
-        exps = expressions.map { |e|
+      def assert_difference(expression, *args, &block)
+        expressions =
+          if expression.is_a?(Hash)
+            message = args[0]
+            expression
+          else
+            difference = args[0] || 1
+            message = args[1]
+            Hash[Array(expression).map { |e| [e, difference] }]
+          end
+
+        exps = expressions.keys.map { |e|
           e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
         }
         before = exps.map(&:call)
 
         retval = yield
 
-        expressions.zip(exps).each_with_index do |(code, e), i|
-          error  = "#{code.inspect} didn't change by #{difference}"
+        expressions.zip(exps, before) do |(code, diff), exp, before_value|
+          error  = "#{code.inspect} didn't change by #{diff}"
           error  = "#{message}.\n#{error}" if message
-          assert_equal(before[i] + difference, e.call, error)
+          assert_equal(before_value + diff, exp.call, error)
         end
 
         retval
diff --git a/activesupport/lib/active_support/testing/parallelization.rb b/activesupport/lib/active_support/testing/parallelization.rb
new file mode 100644
index 0000000000..59c8486f41
--- /dev/null
+++ b/activesupport/lib/active_support/testing/parallelization.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+require "drb"
+require "drb/unix"
+
+module ActiveSupport
+  module Testing
+    class Parallelization # :nodoc:
+      class Server
+        include DRb::DRbUndumped
+
+        def initialize
+          @queue = Queue.new
+        end
+
+        def record(reporter, result)
+          reporter.synchronize do
+            reporter.record(result)
+          end
+        end
+
+        def <<(o)
+          @queue << o
+        end
+
+        def pop; @queue.pop; end
+      end
+
+      @after_fork_hooks = []
+
+      def self.after_fork_hook(&blk)
+        @after_fork_hooks << blk
+      end
+
+      def self.after_fork_hooks
+        @after_fork_hooks
+      end
+
+      @run_cleanup_hooks = []
+
+      def self.run_cleanup_hook(&blk)
+        @run_cleanup_hooks << blk
+      end
+
+      def self.run_cleanup_hooks
+        @run_cleanup_hooks
+      end
+
+      def initialize(queue_size)
+        @queue_size = queue_size
+        @queue      = Server.new
+        @pool       = []
+
+        @url = DRb.start_service("drbunix:", @queue).uri
+      end
+
+      def after_fork(worker)
+        self.class.after_fork_hooks.each do |cb|
+          cb.call(worker)
+        end
+      end
+
+      def run_cleanup(worker)
+        self.class.run_cleanup_hooks.each do |cb|
+          cb.call(worker)
+        end
+      end
+
+      def start
+        @pool = @queue_size.times.map do |worker|
+          fork do
+            DRb.stop_service
+
+            after_fork(worker)
+
+            queue = DRbObject.new_with_uri(@url)
+
+            while job = queue.pop
+              klass    = job[0]
+              method   = job[1]
+              reporter = job[2]
+              result   = Minitest.run_one_method(klass, method)
+
+              queue.record(reporter, result)
+            end
+
+            run_cleanup(worker)
+          end
+        end
+      end
+
+      def <<(work)
+        @queue << work
+      end
+
+      def shutdown
+        @queue_size.times { @queue << nil }
+        @pool.each { |pid| Process.waitpid pid }
+      end
+    end
+  end
+end
diff --git a/activesupport/lib/active_support/testing/time_helpers.rb b/activesupport/lib/active_support/testing/time_helpers.rb
index 998a51a34c..801ea2909b 100644
--- a/activesupport/lib/active_support/testing/time_helpers.rb
+++ b/activesupport/lib/active_support/testing/time_helpers.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "active_support/core_ext/module/redefine_method"
-require "active_support/core_ext/string/strip" # for strip_heredoc
 require "active_support/core_ext/time/calculations"
 require "concurrent/map"
 
@@ -112,7 +111,7 @@ module ActiveSupport
       #   Time.current # => Sat, 09 Nov 2013 15:34:49 EST -05:00
       def travel_to(date_or_time)
         if block_given? && simple_stubs.stubbing(Time, :now)
-          travel_to_nested_block_call = <<-MSG.strip_heredoc
+          travel_to_nested_block_call = <<~MSG
 
       Calling `travel_to` with a block, when we have previously already made a call to `travel_to`, can lead to confusing time stubbing.
 
diff --git a/activesupport/lib/active_support/values/time_zone.rb b/activesupport/lib/active_support/values/time_zone.rb
index 4d81ac939e..9dfaddb825 100644
--- a/activesupport/lib/active_support/values/time_zone.rb
+++ b/activesupport/lib/active_support/values/time_zone.rb
@@ -2,7 +2,6 @@
 
 require "tzinfo"
 require "concurrent/map"
-require "active_support/core_ext/object/blank"
 
 module ActiveSupport
   # The TimeZone class serves as a wrapper around TZInfo::Timezone instances.
@@ -238,7 +237,7 @@ module ActiveSupport
         when Numeric, ActiveSupport::Duration
           arg *= 3600 if arg.abs <= 13
           all.find { |z| z.utc_offset == arg.to_i }
-          else
+        else
           raise ArgumentError, "invalid argument to TimeZone[]: #{arg.inspect}"
         end
       end
@@ -268,11 +267,14 @@ module ActiveSupport
           country = TZInfo::Country.get(code)
           country.zone_identifiers.map do |tz_id|
             if MAPPING.value?(tz_id)
-              self[MAPPING.key(tz_id)]
+              MAPPING.inject([]) do |memo, (key, value)|
+                memo << self[key] if value == tz_id
+                memo
+              end
             else
               create(tz_id, nil, TZInfo::Timezone.new(tz_id))
             end
-          end.sort!
+          end.flatten(1).sort!
         end
 
         def zones_map
diff --git a/activesupport/lib/active_support/values/unicode_tables.dat b/activesupport/lib/active_support/values/unicode_tables.dat
deleted file mode 100644
index f7d9c48bbe..0000000000
--- a/activesupport/lib/active_support/values/unicode_tables.dat
+++ /dev/null
diff --git a/activesupport/lib/active_support/xml_mini.rb b/activesupport/lib/active_support/xml_mini.rb
index ee2048cb54..e42eee07a3 100644
--- a/activesupport/lib/active_support/xml_mini.rb
+++ b/activesupport/lib/active_support/xml_mini.rb
@@ -48,10 +48,6 @@ module ActiveSupport
         "Array"      => "array",
         "Hash"       => "hash"
       }
-
-      # No need to map these on Ruby 2.4+
-      TYPE_NAMES["Fixnum"] = "integer" unless 0.class == Integer
-      TYPE_NAMES["Bignum"] = "integer" unless 0.class == Integer
     end
 
     FORMATTING = {
@@ -83,7 +79,7 @@ module ActiveSupport
         end,
         "boolean"      => Proc.new { |boolean| %w(1 true).include?(boolean.to_s.strip) },
         "string"       => Proc.new { |string|  string.to_s },
-        "yaml"         => Proc.new { |yaml|    YAML::load(yaml) rescue yaml },
+        "yaml"         => Proc.new { |yaml|    YAML.load(yaml) rescue yaml },
         "base64Binary" => Proc.new { |bin|     ::Base64.decode64(bin) },
         "binary"       => Proc.new { |bin, entity| _parse_binary(bin, entity) },
         "file"         => Proc.new { |file, entity| _parse_file(file, entity) }
diff --git a/activesupport/test/array_inquirer_test.rb b/activesupport/test/array_inquirer_test.rb
index d5419b862d..9a260edd8a 100644
--- a/activesupport/test/array_inquirer_test.rb
+++ b/activesupport/test/array_inquirer_test.rb
@@ -9,9 +9,9 @@ class ArrayInquirerTest < ActiveSupport::TestCase
   end
 
   def test_individual
-    assert @array_inquirer.mobile?
-    assert @array_inquirer.tablet?
-    assert_not @array_inquirer.desktop?
+    assert_predicate @array_inquirer, :mobile?
+    assert_predicate @array_inquirer, :tablet?
+    assert_not_predicate @array_inquirer, :desktop?
   end
 
   def test_any
diff --git a/activesupport/test/benchmarkable_test.rb b/activesupport/test/benchmarkable_test.rb
index 424da0a52c..cb7a69cccf 100644
--- a/activesupport/test/benchmarkable_test.rb
+++ b/activesupport/test/benchmarkable_test.rb
@@ -26,7 +26,7 @@ class BenchmarkableTest < ActiveSupport::TestCase
 
   def test_without_block
     assert_raise(LocalJumpError) { benchmark }
-    assert buffer.empty?
+    assert_empty buffer
   end
 
   def test_defaults
diff --git a/activesupport/test/cache/behaviors.rb b/activesupport/test/cache/behaviors.rb
index cb08a10bba..2d39976be3 100644
--- a/activesupport/test/cache/behaviors.rb
+++ b/activesupport/test/cache/behaviors.rb
@@ -3,7 +3,10 @@
 require_relative "behaviors/autoloading_cache_behavior"
 require_relative "behaviors/cache_delete_matched_behavior"
 require_relative "behaviors/cache_increment_decrement_behavior"
+require_relative "behaviors/cache_instrumentation_behavior"
 require_relative "behaviors/cache_store_behavior"
 require_relative "behaviors/cache_store_version_behavior"
+require_relative "behaviors/connection_pool_behavior"
 require_relative "behaviors/encoded_key_cache_behavior"
+require_relative "behaviors/failure_safety_behavior"
 require_relative "behaviors/local_cache_behavior"
diff --git a/activesupport/test/cache/cache_store_write_multi_test.rb b/activesupport/test/cache/behaviors/cache_instrumentation_behavior.rb
index 7d606e3f7b..4e8ff60eb3 100644
--- a/activesupport/test/cache/cache_store_write_multi_test.rb
+++ b/activesupport/test/cache/behaviors/cache_instrumentation_behavior.rb
@@ -1,28 +1,15 @@
 # frozen_string_literal: true
 
-require "abstract_unit"
-require "active_support/cache"
-
-class CacheStoreWriteMultiEntriesStoreProviderInterfaceTest < ActiveSupport::TestCase
-  setup do
-    @cache = ActiveSupport::Cache.lookup_store(:null_store)
-  end
-
-  test "fetch_multi uses write_multi_entries store provider interface" do
+module CacheInstrumentationBehavior
+  def test_fetch_multi_uses_write_multi_entries_store_provider_interface
     assert_called_with(@cache, :write_multi_entries) do
       @cache.fetch_multi "a", "b", "c" do |key|
         key * 2
       end
     end
   end
-end
-
-class CacheStoreWriteMultiInstrumentationTest < ActiveSupport::TestCase
-  setup do
-    @cache = ActiveSupport::Cache.lookup_store(:memory_store)
-  end
 
-  test "instrumentation" do
+  def test_write_multi_instrumentation
     writes = { "a" => "aa", "b" => "bb" }
 
     events = with_instrumentation "write_multi" do
@@ -34,7 +21,7 @@ class CacheStoreWriteMultiInstrumentationTest < ActiveSupport::TestCase
     assert_equal({ "a" => "aa", "b" => "bb" }, events[0].payload[:key])
   end
 
-  test "instrumentation with fetch_multi as super operation" do
+  def test_instrumentation_with_fetch_multi_as_super_operation
     @cache.write("b", "bb")
 
     events = with_instrumentation "read_multi" do
@@ -46,6 +33,17 @@ class CacheStoreWriteMultiInstrumentationTest < ActiveSupport::TestCase
     assert_equal ["b"], events[0].payload[:hits]
   end
 
+  def test_read_multi_instrumentation
+    @cache.write("b", "bb")
+
+    events = with_instrumentation "read_multi" do
+      @cache.read_multi("a", "b") { |key| key * 2 }
+    end
+
+    assert_equal %w[ cache_read_multi.active_support ], events.map(&:name)
+    assert_equal ["b"], events[0].payload[:hits]
+  end
+
   private
     def with_instrumentation(method)
       event_name = "cache_#{method}.active_support"
diff --git a/activesupport/test/cache/behaviors/cache_store_behavior.rb b/activesupport/test/cache/behaviors/cache_store_behavior.rb
index ac37ab6e61..efb57d34a2 100644
--- a/activesupport/test/cache/behaviors/cache_store_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_store_behavior.rb
@@ -113,6 +113,16 @@ module CacheStoreBehavior
     assert_equal("fufu", @cache.read("fu"))
   end
 
+  def test_fetch_multi_without_expires_in
+    @cache.write("foo", "bar")
+    @cache.write("fud", "biz")
+
+    values = @cache.fetch_multi("foo", "fu", "fud", expires_in: nil) { |value| value * 2 }
+
+    assert_equal({ "foo" => "bar", "fu" => "fufu", "fud" => "biz" }, values)
+    assert_equal("fufu", @cache.read("fu"))
+  end
+
   def test_multi_with_objects
     cache_struct = Struct.new(:cache_key, :title)
     foo = cache_struct.new("foo", "FOO!")
diff --git a/activesupport/test/cache/behaviors/cache_store_version_behavior.rb b/activesupport/test/cache/behaviors/cache_store_version_behavior.rb
index c2e4d046af..62c0bb4f6f 100644
--- a/activesupport/test/cache/behaviors/cache_store_version_behavior.rb
+++ b/activesupport/test/cache/behaviors/cache_store_version_behavior.rb
@@ -65,7 +65,7 @@ module CacheStoreVersionBehavior
     m1v2 = ModelWithKeyAndVersion.new("model/1", 2)
 
     @cache.write(m1v1, "bar")
-    assert     @cache.exist?(m1v1)
+    assert @cache.exist?(m1v1)
     assert_not @cache.fetch(m1v2)
   end
 
diff --git a/activesupport/test/cache/behaviors/connection_pool_behavior.rb b/activesupport/test/cache/behaviors/connection_pool_behavior.rb
new file mode 100644
index 0000000000..a0dcc8199c
--- /dev/null
+++ b/activesupport/test/cache/behaviors/connection_pool_behavior.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+module ConnectionPoolBehavior
+  def test_connection_pool
+    Thread.report_on_exception, original_report_on_exception = false, Thread.report_on_exception if Thread.respond_to?(:report_on_exception)
+
+    emulating_latency do
+      begin
+        cache = ActiveSupport::Cache.lookup_store(store, { pool_size: 2, pool_timeout: 1 }.merge(store_options))
+        cache.clear
+
+        threads = []
+
+        assert_raises Timeout::Error do
+          # One of the three threads will fail in 1 second because our pool size
+          # is only two.
+          3.times do
+            threads << Thread.new do
+              cache.read("latency")
+            end
+          end
+
+          threads.each(&:join)
+        end
+      ensure
+        threads.each(&:kill)
+      end
+    end
+  ensure
+    Thread.report_on_exception = original_report_on_exception if Thread.respond_to?(:report_on_exception)
+  end
+
+  def test_no_connection_pool
+    emulating_latency do
+      begin
+        cache = ActiveSupport::Cache.lookup_store(store, store_options)
+        cache.clear
+
+        threads = []
+
+        assert_nothing_raised do
+          # Default connection pool size is 5, assuming 10 will make sure that
+          # the connection pool isn't used at all.
+          10.times do
+            threads << Thread.new do
+              cache.read("latency")
+            end
+          end
+
+          threads.each(&:join)
+        end
+      ensure
+        threads.each(&:kill)
+      end
+    end
+  end
+
+  private
+    def store_options; {}; end
+end
diff --git a/activesupport/test/cache/behaviors/failure_safety_behavior.rb b/activesupport/test/cache/behaviors/failure_safety_behavior.rb
new file mode 100644
index 0000000000..53bda4f942
--- /dev/null
+++ b/activesupport/test/cache/behaviors/failure_safety_behavior.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+module FailureSafetyBehavior
+  def test_fetch_read_failure_returns_nil
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_nil cache.fetch("foo")
+    end
+  end
+
+  def test_fetch_read_failure_does_not_attempt_to_write
+  end
+
+  def test_read_failure_returns_nil
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_nil cache.read("foo")
+    end
+  end
+
+  def test_read_multi_failure_returns_empty_hash
+    @cache.write_multi("foo" => "bar", "baz" => "quux")
+
+    emulating_unavailability do |cache|
+      assert_equal Hash.new, cache.read_multi("foo", "baz")
+    end
+  end
+
+  def test_write_failure_returns_false
+    emulating_unavailability do |cache|
+      assert_equal false, cache.write("foo", "bar")
+    end
+  end
+
+  def test_write_multi_failure_not_raises
+    emulating_unavailability do |cache|
+      assert_nothing_raised do
+        cache.write_multi("foo" => "bar", "baz" => "quux")
+      end
+    end
+  end
+
+  def test_fetch_multi_failure_returns_fallback_results
+    @cache.write_multi("foo" => "bar", "baz" => "quux")
+
+    emulating_unavailability do |cache|
+      fetched = cache.fetch_multi("foo", "baz") { |k| "unavailable" }
+      assert_equal Hash["foo" => "unavailable", "baz" => "unavailable"], fetched
+    end
+  end
+
+  def test_delete_failure_returns_false
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_equal false, cache.delete("foo")
+    end
+  end
+
+  def test_exist_failure_returns_false
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert !cache.exist?("foo")
+    end
+  end
+
+  def test_increment_failure_returns_nil
+    @cache.write("foo", 1, raw: true)
+
+    emulating_unavailability do |cache|
+      assert_nil cache.increment("foo")
+    end
+  end
+
+  def test_decrement_failure_returns_nil
+    @cache.write("foo", 1, raw: true)
+
+    emulating_unavailability do |cache|
+      assert_nil cache.decrement("foo")
+    end
+  end
+
+  def test_clear_failure_returns_nil
+    emulating_unavailability do |cache|
+      assert_nil cache.clear
+    end
+  end
+end
diff --git a/activesupport/test/cache/behaviors/local_cache_behavior.rb b/activesupport/test/cache/behaviors/local_cache_behavior.rb
index f7302df4c8..363f2d1084 100644
--- a/activesupport/test/cache/behaviors/local_cache_behavior.rb
+++ b/activesupport/test/cache/behaviors/local_cache_behavior.rb
@@ -119,6 +119,16 @@ module LocalCacheBehavior
     end
   end
 
+  def test_local_cache_of_fetch_multi
+    @cache.with_local_cache do
+      @cache.fetch_multi("foo", "bar") { |_key| true }
+      @peek.delete("foo")
+      @peek.delete("bar")
+      assert_equal true, @cache.read("foo")
+      assert_equal true, @cache.read("bar")
+    end
+  end
+
   def test_middleware
     app = lambda { |env|
       result = @cache.write("foo", "bar")
diff --git a/activesupport/test/cache/cache_store_logger_test.rb b/activesupport/test/cache/cache_store_logger_test.rb
index 1af6893cc9..4648b2d361 100644
--- a/activesupport/test/cache/cache_store_logger_test.rb
+++ b/activesupport/test/cache/cache_store_logger_test.rb
@@ -13,7 +13,7 @@ class CacheStoreLoggerTest < ActiveSupport::TestCase
 
   def test_logging
     @cache.fetch("foo") { "bar" }
-    assert @buffer.string.present?
+    assert_predicate @buffer.string, :present?
   end
 
   def test_log_with_string_namespace
@@ -31,6 +31,6 @@ class CacheStoreLoggerTest < ActiveSupport::TestCase
 
   def test_mute_logging
     @cache.mute { @cache.fetch("foo") { "bar" } }
-    assert @buffer.string.blank?
+    assert_predicate @buffer.string, :blank?
   end
 end
diff --git a/activesupport/test/cache/stores/file_store_test.rb b/activesupport/test/cache/stores/file_store_test.rb
index 66231b0a82..c3c35a7bcc 100644
--- a/activesupport/test/cache/stores/file_store_test.rb
+++ b/activesupport/test/cache/stores/file_store_test.rb
@@ -30,6 +30,7 @@ class FileStoreTest < ActiveSupport::TestCase
   include LocalCacheBehavior
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
+  include CacheInstrumentationBehavior
   include AutoloadingCacheBehavior
 
   def test_clear
@@ -98,13 +99,13 @@ class FileStoreTest < ActiveSupport::TestCase
     end
     assert File.exist?(cache_dir), "Parent of top level cache dir was deleted!"
     assert File.exist?(sub_cache_dir), "Top level cache dir was deleted!"
-    assert Dir.entries(sub_cache_dir).reject { |f| ActiveSupport::Cache::FileStore::EXCLUDED_DIRS.include?(f) }.empty?
+    assert_empty Dir.entries(sub_cache_dir).reject { |f| ActiveSupport::Cache::FileStore::EXCLUDED_DIRS.include?(f) }
   end
 
   def test_log_exception_when_cache_read_fails
     File.stub(:exist?, -> { raise StandardError.new("failed") }) do
       @cache.send(:read_entry, "winston", {})
-      assert @buffer.string.present?
+      assert_predicate @buffer.string, :present?
     end
   end
 
diff --git a/activesupport/test/cache/stores/mem_cache_store_test.rb b/activesupport/test/cache/stores/mem_cache_store_test.rb
index 99624caf8a..f426a37c66 100644
--- a/activesupport/test/cache/stores/mem_cache_store_test.rb
+++ b/activesupport/test/cache/stores/mem_cache_store_test.rb
@@ -5,6 +5,24 @@ require "active_support/cache"
 require_relative "../behaviors"
 require "dalli"
 
+# Emulates a latency on Dalli's back-end for the key latency to facilitate
+# connection pool testing.
+class SlowDalliClient < Dalli::Client
+  def get(key, options = {})
+    if key =~ /latency/
+      sleep 3
+    else
+      super
+    end
+  end
+end
+
+class UnavailableDalliServer < Dalli::Server
+  def alive?
+    false
+  end
+end
+
 class MemCacheStoreTest < ActiveSupport::TestCase
   begin
     ss = Dalli::Client.new("localhost:11211").stats
@@ -31,8 +49,11 @@ class MemCacheStoreTest < ActiveSupport::TestCase
   include CacheStoreVersionBehavior
   include LocalCacheBehavior
   include CacheIncrementDecrementBehavior
+  include CacheInstrumentationBehavior
   include EncodedKeyCacheBehavior
   include AutoloadingCacheBehavior
+  include ConnectionPoolBehavior
+  include FailureSafetyBehavior
 
   def test_raw_values
     cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
@@ -89,4 +110,30 @@ class MemCacheStoreTest < ActiveSupport::TestCase
     value << "bingo"
     assert_not_equal value, @cache.read("foo")
   end
+
+  private
+
+    def store
+      :mem_cache_store
+    end
+
+    def emulating_latency
+      old_client = Dalli.send(:remove_const, :Client)
+      Dalli.const_set(:Client, SlowDalliClient)
+
+      yield
+    ensure
+      Dalli.send(:remove_const, :Client)
+      Dalli.const_set(:Client, old_client)
+    end
+
+    def emulating_unavailability
+      old_server = Dalli.send(:remove_const, :Server)
+      Dalli.const_set(:Server, UnavailableDalliServer)
+
+      yield ActiveSupport::Cache::MemCacheStore.new
+    ensure
+      Dalli.send(:remove_const, :Server)
+      Dalli.const_set(:Server, old_server)
+    end
 end
diff --git a/activesupport/test/cache/stores/memory_store_test.rb b/activesupport/test/cache/stores/memory_store_test.rb
index 3981f05331..72fafc187b 100644
--- a/activesupport/test/cache/stores/memory_store_test.rb
+++ b/activesupport/test/cache/stores/memory_store_test.rb
@@ -14,6 +14,7 @@ class MemoryStoreTest < ActiveSupport::TestCase
   include CacheStoreVersionBehavior
   include CacheDeleteMatchedBehavior
   include CacheIncrementDecrementBehavior
+  include CacheInstrumentationBehavior
 
   def test_prune_size
     @cache.write(1, "aaaaaaaaaa") && sleep(0.001)
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
index 7f684f7a0f..375993a632 100644
--- a/activesupport/test/cache/stores/redis_cache_store_test.rb
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -5,7 +5,27 @@ require "active_support/cache"
 require "active_support/cache/redis_cache_store"
 require_relative "../behaviors"
 
+driver_name = %w[ ruby hiredis ].include?(ENV["REDIS_DRIVER"]) ? ENV["REDIS_DRIVER"] : "hiredis"
+driver = Object.const_get("Redis::Connection::#{driver_name.camelize}")
+
+Redis::Connection.drivers.clear
+Redis::Connection.drivers.append(driver)
+
+# Emulates a latency on Redis's back-end for the key latency to facilitate
+# connection pool testing.
+class SlowRedis < Redis
+  def get(key, options = {})
+    if key =~ /latency/
+      sleep 3
+    else
+      super
+    end
+  end
+end
+
 module ActiveSupport::Cache::RedisCacheStoreTests
+  DRIVER = %w[ ruby hiredis ].include?(ENV["REDIS_DRIVER"]) ? ENV["REDIS_DRIVER"] : "hiredis"
+
   class LookupTest < ActiveSupport::TestCase
     test "may be looked up as :redis_cache_store" do
       assert_kind_of ActiveSupport::Cache::RedisCacheStore,
@@ -18,7 +38,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       assert_called_with Redis, :new, [
         url: nil,
         connect_timeout: 20, read_timeout: 1, write_timeout: 1,
-        reconnect_attempts: 0,
+        reconnect_attempts: 0, driver: DRIVER
       ] do
         build
       end
@@ -28,7 +48,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       assert_called_with Redis, :new, [
         url: nil,
         connect_timeout: 20, read_timeout: 1, write_timeout: 1,
-        reconnect_attempts: 0,
+        reconnect_attempts: 0, driver: DRIVER
       ] do
         build url: []
       end
@@ -38,7 +58,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       assert_called_with Redis, :new, [
         url: "redis://localhost:6379/0",
         connect_timeout: 20, read_timeout: 1, write_timeout: 1,
-        reconnect_attempts: 0,
+        reconnect_attempts: 0, driver: DRIVER
       ] do
         build url: "redis://localhost:6379/0"
       end
@@ -48,7 +68,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       assert_called_with Redis, :new, [
         url: "redis://localhost:6379/0",
         connect_timeout: 20, read_timeout: 1, write_timeout: 1,
-        reconnect_attempts: 0,
+        reconnect_attempts: 0, driver: DRIVER
       ] do
         build url: %w[ redis://localhost:6379/0 ]
       end
@@ -58,10 +78,10 @@ module ActiveSupport::Cache::RedisCacheStoreTests
       assert_called_with Redis, :new, [
         [ url: "redis://localhost:6379/0",
           connect_timeout: 20, read_timeout: 1, write_timeout: 1,
-          reconnect_attempts: 0 ],
+          reconnect_attempts: 0, driver: DRIVER ],
         [ url: "redis://localhost:6379/1",
           connect_timeout: 20, read_timeout: 1, write_timeout: 1,
-          reconnect_attempts: 0 ],
+          reconnect_attempts: 0, driver: DRIVER ],
       ], returns: Redis.new do
         @cache = build url: %w[ redis://localhost:6379/0 redis://localhost:6379/1 ]
         assert_kind_of ::Redis::Distributed, @cache.redis
@@ -77,7 +97,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
 
     private
       def build(**kwargs)
-        ActiveSupport::Cache::RedisCacheStore.new(**kwargs).tap do |cache|
+        ActiveSupport::Cache::RedisCacheStore.new(driver: DRIVER, **kwargs).tap do |cache|
           cache.redis
         end
       end
@@ -87,11 +107,11 @@ module ActiveSupport::Cache::RedisCacheStoreTests
     setup do
       @namespace = "namespace"
 
-      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, expires_in: 60)
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, expires_in: 60, driver: DRIVER)
       # @cache.logger = Logger.new($stdout)  # For test debugging
 
       # For LocalCacheBehavior tests
-      @peek = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace)
+      @peek = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, namespace: @namespace, driver: DRIVER)
     end
 
     teardown do
@@ -105,7 +125,43 @@ module ActiveSupport::Cache::RedisCacheStoreTests
     include CacheStoreVersionBehavior
     include LocalCacheBehavior
     include CacheIncrementDecrementBehavior
+    include CacheInstrumentationBehavior
     include AutoloadingCacheBehavior
+
+    def test_fetch_multi_uses_redis_mget
+      assert_called(@cache.redis, :mget, returns: []) do
+        @cache.fetch_multi("a", "b", "c") do |key|
+          key * 2
+        end
+      end
+    end
+  end
+
+  class ConnectionPoolBehaviourTest < StoreTest
+    include ConnectionPoolBehavior
+
+    private
+
+      def store
+        :redis_cache_store
+      end
+
+      def emulating_latency
+        old_redis = Object.send(:remove_const, :Redis)
+        Object.const_set(:Redis, SlowRedis)
+
+        yield
+      ensure
+        Object.send(:remove_const, :Redis)
+        Object.const_set(:Redis, old_redis)
+      end
+  end
+
+  class RedisDistributedConnectionPoolBehaviourTest < ConnectionPoolBehaviourTest
+    private
+      def store_options
+        { url: %w[ redis://localhost:6379/0 redis://localhost:6379/0 ] }
+      end
   end
 
   # Separate test class so we can omit the namespace which causes expected,
@@ -114,7 +170,7 @@ module ActiveSupport::Cache::RedisCacheStoreTests
     include EncodedKeyCacheBehavior
 
     setup do
-      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1)
+      @cache = ActiveSupport::Cache::RedisCacheStore.new(timeout: 0.1, driver: DRIVER)
       @cache.logger = nil
     end
   end
@@ -122,15 +178,26 @@ module ActiveSupport::Cache::RedisCacheStoreTests
   class StoreAPITest < StoreTest
   end
 
-  class FailureSafetyTest < StoreTest
-    test "fetch read failure returns nil" do
+  class UnavailableRedisClient < Redis::Client
+    def ensure_connected
+      raise Redis::BaseConnectionError
     end
+  end
 
-    test "fetch read failure does not attempt to write" do
-    end
+  class FailureSafetyTest < StoreTest
+    include FailureSafetyBehavior
 
-    test "write failure returns nil" do
-    end
+    private
+
+      def emulating_unavailability
+        old_client = Redis.send(:remove_const, :Client)
+        Redis.const_set(:Client, UnavailableRedisClient)
+
+        yield ActiveSupport::Cache::RedisCacheStore.new
+      ensure
+        Redis.send(:remove_const, :Client)
+        Redis.const_set(:Client, old_client)
+      end
   end
 
   class DeleteMatchedTest < StoreTest
diff --git a/activesupport/test/callback_inheritance_test.rb b/activesupport/test/callback_inheritance_test.rb
index 67813a749e..015e17deb9 100644
--- a/activesupport/test/callback_inheritance_test.rb
+++ b/activesupport/test/callback_inheritance_test.rb
@@ -164,10 +164,10 @@ end
 class DynamicInheritedCallbacks < ActiveSupport::TestCase
   def test_callbacks_looks_to_the_superclass_before_running
     child = EmptyChild.new.dispatch
-    assert !child.performed?
+    assert_not_predicate child, :performed?
     EmptyParent.set_callback :dispatch, :before, :perform!
     child = EmptyChild.new.dispatch
-    assert child.performed?
+    assert_predicate child, :performed?
   end
 
   def test_callbacks_should_be_performed_once_in_child_class
diff --git a/activesupport/test/callbacks_test.rb b/activesupport/test/callbacks_test.rb
index 30f1632460..6c7643ed72 100644
--- a/activesupport/test/callbacks_test.rb
+++ b/activesupport/test/callbacks_test.rb
@@ -482,10 +482,9 @@ module CallbacksTest
         "block in run_callbacks",
         "tweedle_dum",
         "block in run_callbacks",
-        ("call" if RUBY_VERSION < "2.3"),
         "run_callbacks",
         "save"
-      ].compact, call_stack.map(&:label)
+      ], call_stack.map(&:label)
     end
 
     def test_short_call_stack
diff --git a/activesupport/test/class_cache_test.rb b/activesupport/test/class_cache_test.rb
index 7b97028e8c..8cfcaedafd 100644
--- a/activesupport/test/class_cache_test.rb
+++ b/activesupport/test/class_cache_test.rb
@@ -11,17 +11,17 @@ module ActiveSupport
       end
 
       def test_empty?
-        assert @cache.empty?
+        assert_empty @cache
         @cache.store(ClassCacheTest)
-        assert !@cache.empty?
+        assert_not_empty @cache
       end
 
       def test_clear!
-        assert @cache.empty?
+        assert_empty @cache
         @cache.store(ClassCacheTest)
-        assert !@cache.empty?
+        assert_not_empty @cache
         @cache.clear!
-        assert @cache.empty?
+        assert_empty @cache
       end
 
       def test_set_key
@@ -40,29 +40,29 @@ module ActiveSupport
       end
 
       def test_get_constantizes
-        assert @cache.empty?
+        assert_empty @cache
         assert_equal ClassCacheTest, @cache.get(ClassCacheTest.name)
       end
 
       def test_get_constantizes_fails_on_invalid_names
-        assert @cache.empty?
+        assert_empty @cache
         assert_raise NameError do
           @cache.get("OmgTotallyInvalidConstantName")
         end
       end
 
       def test_get_alias
-        assert @cache.empty?
+        assert_empty @cache
         assert_equal @cache[ClassCacheTest.name], @cache.get(ClassCacheTest.name)
       end
 
       def test_safe_get_constantizes
-        assert @cache.empty?
+        assert_empty @cache
         assert_equal ClassCacheTest, @cache.safe_get(ClassCacheTest.name)
       end
 
       def test_safe_get_constantizes_doesnt_fail_on_invalid_names
-        assert @cache.empty?
+        assert_empty @cache
         assert_nil @cache.safe_get("OmgTotallyInvalidConstantName")
       end
 
diff --git a/activesupport/test/concern_test.rb b/activesupport/test/concern_test.rb
index ef75a320d1..98d8f3ee0d 100644
--- a/activesupport/test/concern_test.rb
+++ b/activesupport/test/concern_test.rb
@@ -91,7 +91,7 @@ class ConcernTest < ActiveSupport::TestCase
       end
     end
     @klass.include test_module
-    assert_equal false, Object.respond_to?(:test)
+    assert_not_respond_to Object, :test
     Qux.class_eval do
       remove_const :ClassMethods
     end
diff --git a/activesupport/test/configurable_test.rb b/activesupport/test/configurable_test.rb
index 10719596df..1cf40261dc 100644
--- a/activesupport/test/configurable_test.rb
+++ b/activesupport/test/configurable_test.rb
@@ -43,11 +43,11 @@ class ConfigurableActiveSupport < ActiveSupport::TestCase
   test "configuration accessors are not available on instance" do
     instance = Parent.new
 
-    assert !instance.respond_to?(:bar)
-    assert !instance.respond_to?(:bar=)
+    assert_not_respond_to instance, :bar
+    assert_not_respond_to instance, :bar=
 
-    assert !instance.respond_to?(:baz)
-    assert !instance.respond_to?(:baz=)
+    assert_not_respond_to instance, :baz
+    assert_not_respond_to instance, :baz=
   end
 
   test "configuration accessors can take a default value" do
diff --git a/activesupport/test/core_ext/array/grouping_test.rb b/activesupport/test/core_ext/array/grouping_test.rb
index c182b91826..37111a5d7d 100644
--- a/activesupport/test/core_ext/array/grouping_test.rb
+++ b/activesupport/test/core_ext/array/grouping_test.rb
@@ -4,15 +4,6 @@ require "abstract_unit"
 require "active_support/core_ext/array"
 
 class GroupingTest < ActiveSupport::TestCase
-  def setup
-    # In Ruby < 2.4, test we avoid Integer#/ (redefined by mathn)
-    Fixnum.send :private, :/ unless 0.class == Integer
-  end
-
-  def teardown
-    Fixnum.send :public, :/ unless 0.class == Integer
-  end
-
   def test_in_groups_of_with_perfect_fit
     groups = []
     ("a".."i").to_a.in_groups_of(3) do |group|
diff --git a/activesupport/test/core_ext/class_test.rb b/activesupport/test/core_ext/class_test.rb
index 9cc006fc63..5ea288738e 100644
--- a/activesupport/test/core_ext/class_test.rb
+++ b/activesupport/test/core_ext/class_test.rb
@@ -30,11 +30,11 @@ class ClassTest < ActiveSupport::TestCase
 
   def test_descendants_excludes_singleton_classes
     klass = Parent.new.singleton_class
-    refute Parent.descendants.include?(klass), "descendants should not include singleton classes"
+    assert_not Parent.descendants.include?(klass), "descendants should not include singleton classes"
   end
 
   def test_subclasses_excludes_singleton_classes
     klass = Parent.new.singleton_class
-    refute Parent.subclasses.include?(klass), "subclasses should not include singleton classes"
+    assert_not Parent.subclasses.include?(klass), "subclasses should not include singleton classes"
   end
 end
diff --git a/activesupport/test/core_ext/date_and_time_behavior.rb b/activesupport/test/core_ext/date_and_time_behavior.rb
index 1176ed647a..1422f135a8 100644
--- a/activesupport/test/core_ext/date_and_time_behavior.rb
+++ b/activesupport/test/core_ext/date_and_time_behavior.rb
@@ -361,28 +361,28 @@ module DateAndTimeBehavior
   end
 
   def test_on_weekend_on_saturday
-    assert date_time_init(2015, 1, 3, 0, 0, 0).on_weekend?
-    assert date_time_init(2015, 1, 3, 15, 15, 10).on_weekend?
+    assert_predicate date_time_init(2015, 1, 3, 0, 0, 0), :on_weekend?
+    assert_predicate date_time_init(2015, 1, 3, 15, 15, 10), :on_weekend?
   end
 
   def test_on_weekend_on_sunday
-    assert date_time_init(2015, 1, 4, 0, 0, 0).on_weekend?
-    assert date_time_init(2015, 1, 4, 15, 15, 10).on_weekend?
+    assert_predicate date_time_init(2015, 1, 4, 0, 0, 0), :on_weekend?
+    assert_predicate date_time_init(2015, 1, 4, 15, 15, 10), :on_weekend?
   end
 
   def test_on_weekend_on_monday
-    assert_not date_time_init(2015, 1, 5, 0, 0, 0).on_weekend?
-    assert_not date_time_init(2015, 1, 5, 15, 15, 10).on_weekend?
+    assert_not_predicate date_time_init(2015, 1, 5, 0, 0, 0), :on_weekend?
+    assert_not_predicate date_time_init(2015, 1, 5, 15, 15, 10), :on_weekend?
   end
 
   def test_on_weekday_on_sunday
-    assert_not date_time_init(2015, 1, 4, 0, 0, 0).on_weekday?
-    assert_not date_time_init(2015, 1, 4, 15, 15, 10).on_weekday?
+    assert_not_predicate date_time_init(2015, 1, 4, 0, 0, 0), :on_weekday?
+    assert_not_predicate date_time_init(2015, 1, 4, 15, 15, 10), :on_weekday?
   end
 
   def test_on_weekday_on_monday
-    assert date_time_init(2015, 1, 5, 0, 0, 0).on_weekday?
-    assert date_time_init(2015, 1, 5, 15, 15, 10).on_weekday?
+    assert_predicate date_time_init(2015, 1, 5, 0, 0, 0), :on_weekday?
+    assert_predicate date_time_init(2015, 1, 5, 15, 15, 10), :on_weekday?
   end
 
   def with_bw_default(bw = :monday)
diff --git a/activesupport/test/core_ext/date_ext_test.rb b/activesupport/test/core_ext/date_ext_test.rb
index 23d17956df..b8652884ce 100644
--- a/activesupport/test/core_ext/date_ext_test.rb
+++ b/activesupport/test/core_ext/date_ext_test.rb
@@ -386,11 +386,11 @@ end
 
 class DateExtBehaviorTest < ActiveSupport::TestCase
   def test_date_acts_like_date
-    assert Date.new.acts_like_date?
+    assert_predicate Date.new, :acts_like_date?
   end
 
   def test_blank?
-    assert_not Date.new.blank?
+    assert_not_predicate Date.new, :blank?
   end
 
   def test_freeze_doesnt_clobber_memoized_instance_methods
diff --git a/activesupport/test/core_ext/date_time_ext_test.rb b/activesupport/test/core_ext/date_time_ext_test.rb
index f4c9dfcb25..894fb80cba 100644
--- a/activesupport/test/core_ext/date_time_ext_test.rb
+++ b/activesupport/test/core_ext/date_time_ext_test.rb
@@ -315,15 +315,15 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_date
-    assert DateTime.new.acts_like_date?
+    assert_predicate DateTime.new, :acts_like_date?
   end
 
   def test_acts_like_time
-    assert DateTime.new.acts_like_time?
+    assert_predicate DateTime.new, :acts_like_time?
   end
 
   def test_blank?
-    assert_not DateTime.new.blank?
+    assert_not_predicate DateTime.new, :blank?
   end
 
   def test_utc?
@@ -363,45 +363,45 @@ class DateTimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_compare_with_time
-    assert_equal  1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_datetime
-    assert_equal  1, DateTime.civil(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, DateTime.civil(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, DateTime.civil(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, DateTime.civil(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, DateTime.civil(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_time_with_zone
-    assert_equal  1, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
-    assert_equal  0, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
+    assert_equal 1, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
+    assert_equal 0, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
     assert_equal(-1, DateTime.civil(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone["UTC"]))
   end
 
   def test_compare_with_string
-    assert_equal   1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59).to_s
-    assert_equal   0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
+    assert_equal 1, DateTime.civil(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59).to_s
+    assert_equal 0, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
     assert_equal(-1, DateTime.civil(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1).to_s)
     assert_nil DateTime.civil(2000) <=> "Invalid as Time"
   end
 
   def test_compare_with_integer
-    assert_equal  1, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440587
-    assert_equal  0, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440588
+    assert_equal 1, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440587
+    assert_equal 0, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440588
     assert_equal(-1, DateTime.civil(1970, 1, 1, 12, 0, 0) <=> 2440589)
   end
 
   def test_compare_with_float
-    assert_equal  1, DateTime.civil(1970) <=> 2440586.5
-    assert_equal  0, DateTime.civil(1970) <=> 2440587.5
+    assert_equal 1, DateTime.civil(1970) <=> 2440586.5
+    assert_equal 0, DateTime.civil(1970) <=> 2440587.5
     assert_equal(-1, DateTime.civil(1970) <=> 2440588.5)
   end
 
   def test_compare_with_rational
-    assert_equal  1, DateTime.civil(1970) <=> Rational(4881173, 2)
-    assert_equal  0, DateTime.civil(1970) <=> Rational(4881175, 2)
+    assert_equal 1, DateTime.civil(1970) <=> Rational(4881173, 2)
+    assert_equal 0, DateTime.civil(1970) <=> Rational(4881175, 2)
     assert_equal(-1, DateTime.civil(1970) <=> Rational(4881177, 2))
   end
 
diff --git a/activesupport/test/core_ext/duration_test.rb b/activesupport/test/core_ext/duration_test.rb
index 4a02f27def..8f6befe809 100644
--- a/activesupport/test/core_ext/duration_test.rb
+++ b/activesupport/test/core_ext/duration_test.rb
@@ -5,6 +5,7 @@ require "active_support/inflector"
 require "active_support/time"
 require "active_support/json"
 require "time_zone_test_helpers"
+require "yaml"
 
 class DurationTest < ActiveSupport::TestCase
   include TimeZoneTestHelpers
@@ -23,7 +24,7 @@ class DurationTest < ActiveSupport::TestCase
   end
 
   def test_instance_of
-    assert 1.minute.instance_of?(1.class)
+    assert 1.minute.instance_of?(Integer)
     assert 2.days.instance_of?(ActiveSupport::Duration)
     assert !3.second.instance_of?(Numeric)
   end
@@ -642,6 +643,12 @@ class DurationTest < ActiveSupport::TestCase
     assert_equal time + d1, time + d2
   end
 
+  def test_durations_survive_yaml_serialization
+    d1 = YAML.load(YAML.dump(10.minutes))
+    assert_equal 600, d1.to_i
+    assert_equal 660, (d1 + 60).to_i
+  end
+
   private
     def eastern_time_zone
       if Gem.win_platform?
diff --git a/activesupport/test/core_ext/hash/transform_values_test.rb b/activesupport/test/core_ext/hash/transform_values_test.rb
index d34b7fa7b9..e481b5e4a9 100644
--- a/activesupport/test/core_ext/hash/transform_values_test.rb
+++ b/activesupport/test/core_ext/hash/transform_values_test.rb
@@ -2,25 +2,16 @@
 
 require "abstract_unit"
 require "active_support/core_ext/hash/indifferent_access"
-require "active_support/core_ext/hash/transform_values"
 
-class TransformValuesTest < ActiveSupport::TestCase
-  test "transform_values returns a new hash with the values computed from the block" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal({ a: "a", b: "b" }, original)
-    assert_equal({ a: "a!", b: "b!" }, mapped)
-  end
-
-  test "transform_values! modifies the values of the original" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values! { |v| v + "!" }
-
-    assert_equal({ a: "a!", b: "b!" }, original)
-    assert_same original, mapped
+class TransformValuesDeprecatedRequireTest < ActiveSupport::TestCase
+  test "requiring transform_values is deprecated" do
+    assert_deprecated do
+      require "active_support/core_ext/hash/transform_values"
+    end
   end
+end
 
+class IndifferentTransformValuesTest < ActiveSupport::TestCase
   test "indifferent access is still indifferent after mapping values" do
     original = { a: "a", b: "b" }.with_indifferent_access
     mapped = original.transform_values { |v| v + "!" }
@@ -28,50 +19,4 @@ class TransformValuesTest < ActiveSupport::TestCase
     assert_equal "a!", mapped[:a]
     assert_equal "a!", mapped["a"]
   end
-
-  # This is to be consistent with the behavior of Ruby's built in methods
-  # (e.g. #select, #reject) as of 2.2
-  test "default values do not persist during mapping" do
-    original = Hash.new("foo")
-    original[:a] = "a"
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal "a!", mapped[:a]
-    assert_nil mapped[:b]
-  end
-
-  test "default procs do not persist after mapping" do
-    original = Hash.new { "foo" }
-    original[:a] = "a"
-    mapped = original.transform_values { |v| v + "!" }
-
-    assert_equal "a!", mapped[:a]
-    assert_nil mapped[:b]
-  end
-
-  test "transform_values returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_values
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_values! returns a sized Enumerator if no block is given" do
-    original = { a: "a", b: "b" }
-    enumerator = original.transform_values!
-    assert_equal original.size, enumerator.size
-    assert_equal Enumerator, enumerator.class
-  end
-
-  test "transform_values is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    mapped = original.transform_values.with_index { |v, i| [v, i].join }
-    assert_equal({ a: "a0", b: "b1" }, mapped)
-  end
-
-  test "transform_values! is chainable with Enumerable methods" do
-    original = { a: "a", b: "b" }
-    original.transform_values!.with_index { |v, i| [v, i].join }
-    assert_equal({ a: "a0", b: "b1" }, original)
-  end
 end
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 17952e9fc7..50b811e79f 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -1061,7 +1061,7 @@ class HashToXmlTest < ActiveSupport::TestCase
       </alert>
     XML
     alert_at = Hash.from_xml(alert_xml)["alert"]["alert_at"]
-    assert alert_at.utc?
+    assert_predicate alert_at, :utc?
     assert_equal Time.utc(2008, 2, 10, 15, 30, 45), alert_at
   end
 
@@ -1072,7 +1072,7 @@ class HashToXmlTest < ActiveSupport::TestCase
       </alert>
     XML
     alert_at = Hash.from_xml(alert_xml)["alert"]["alert_at"]
-    assert alert_at.utc?
+    assert_predicate alert_at, :utc?
     assert_equal Time.utc(2008, 2, 10, 15, 30, 45), alert_at
   end
 
@@ -1083,7 +1083,7 @@ class HashToXmlTest < ActiveSupport::TestCase
       </alert>
     XML
     alert_at = Hash.from_xml(alert_xml)["alert"]["alert_at"]
-    assert alert_at.utc?
+    assert_predicate alert_at, :utc?
     assert_equal 2050,  alert_at.year
     assert_equal 2,     alert_at.month
     assert_equal 10,    alert_at.day
diff --git a/activesupport/test/core_ext/module/anonymous_test.rb b/activesupport/test/core_ext/module/anonymous_test.rb
index 606f22c9b5..e03c217015 100644
--- a/activesupport/test/core_ext/module/anonymous_test.rb
+++ b/activesupport/test/core_ext/module/anonymous_test.rb
@@ -5,12 +5,12 @@ require "active_support/core_ext/module/anonymous"
 
 class AnonymousTest < ActiveSupport::TestCase
   test "an anonymous class or module are anonymous" do
-    assert Module.new.anonymous?
-    assert Class.new.anonymous?
+    assert_predicate Module.new, :anonymous?
+    assert_predicate Class.new, :anonymous?
   end
 
   test "a named class or module are not anonymous" do
-    assert !Kernel.anonymous?
-    assert !Object.anonymous?
+    assert_not_predicate Kernel, :anonymous?
+    assert_not_predicate Object, :anonymous?
   end
 end
diff --git a/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb b/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb
index e0fbd1002c..e0e331fc91 100644
--- a/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb
+++ b/activesupport/test/core_ext/module/attribute_accessor_per_thread_test.rb
@@ -43,22 +43,22 @@ class ModuleAttributeAccessorPerThreadTest < ActiveSupport::TestCase
       assert_respond_to @class, :foo
       assert_respond_to @class, :foo=
       assert_respond_to @object, :bar
-      assert !@object.respond_to?(:bar=)
+      assert_not_respond_to @object, :bar=
     end.join
   end
 
   def test_should_not_create_instance_reader
     Thread.new do
       assert_respond_to @class, :shaq
-      assert !@object.respond_to?(:shaq)
+      assert_not_respond_to @object, :shaq
     end.join
   end
 
   def test_should_not_create_instance_accessors
     Thread.new do
       assert_respond_to @class, :camp
-      assert !@object.respond_to?(:camp)
-      assert !@object.respond_to?(:camp=)
+      assert_not_respond_to @object, :camp
+      assert_not_respond_to @object, :camp=
     end.join
   end
 
diff --git a/activesupport/test/core_ext/module/attribute_accessor_test.rb b/activesupport/test/core_ext/module/attribute_accessor_test.rb
index f1d6859a88..33c583947a 100644
--- a/activesupport/test/core_ext/module/attribute_accessor_test.rb
+++ b/activesupport/test/core_ext/module/attribute_accessor_test.rb
@@ -65,18 +65,18 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
     assert_respond_to @module, :foo
     assert_respond_to @module, :foo=
     assert_respond_to @object, :bar
-    assert !@object.respond_to?(:bar=)
+    assert_not_respond_to @object, :bar=
   end
 
   def test_should_not_create_instance_reader
     assert_respond_to @module, :shaq
-    assert !@object.respond_to?(:shaq)
+    assert_not_respond_to @object, :shaq
   end
 
   def test_should_not_create_instance_accessors
     assert_respond_to @module, :camp
-    assert !@object.respond_to?(:camp)
-    assert !@object.respond_to?(:camp=)
+    assert_not_respond_to @object, :camp
+    assert_not_respond_to @object, :camp=
   end
 
   def test_should_raise_name_error_if_attribute_name_is_invalid
diff --git a/activesupport/test/core_ext/module/attribute_aliasing_test.rb b/activesupport/test/core_ext/module/attribute_aliasing_test.rb
index 187a0f4da2..81aac224f9 100644
--- a/activesupport/test/core_ext/module/attribute_aliasing_test.rb
+++ b/activesupport/test/core_ext/module/attribute_aliasing_test.rb
@@ -30,15 +30,15 @@ class AttributeAliasingTest < ActiveSupport::TestCase
   def test_attribute_alias
     e = AttributeAliasing::Email.new
 
-    assert !e.subject?
+    assert_not_predicate e, :subject?
 
     e.title = "Upgrade computer"
     assert_equal "Upgrade computer", e.subject
-    assert e.subject?
+    assert_predicate e, :subject?
 
     e.subject = "We got a long way to go"
     assert_equal "We got a long way to go", e.title
-    assert e.title?
+    assert_predicate e, :title?
   end
 
   def test_aliasing_to_uppercase_attributes
@@ -47,15 +47,15 @@ class AttributeAliasingTest < ActiveSupport::TestCase
     # to more sensible ones, everything goes *foof*.
     e = AttributeAliasing::Email.new
 
-    assert !e.body?
-    assert !e.Data?
+    assert_not_predicate e, :body?
+    assert_not_predicate e, :Data?
 
     e.body = "No, really, this is not a joke."
     assert_equal "No, really, this is not a joke.", e.Data
-    assert e.Data?
+    assert_predicate e, :Data?
 
     e.Data = "Uppercased methods are the suck"
     assert_equal "Uppercased methods are the suck", e.body
-    assert e.body?
+    assert_predicate e, :body?
   end
 end
diff --git a/activesupport/test/core_ext/module/concerning_test.rb b/activesupport/test/core_ext/module/concerning_test.rb
index 192c3d5a9c..969434766f 100644
--- a/activesupport/test/core_ext/module/concerning_test.rb
+++ b/activesupport/test/core_ext/module/concerning_test.rb
@@ -55,10 +55,10 @@ class ModuleConcernTest < ActiveSupport::TestCase
   end
 
   def test_using_class_methods_blocks_instead_of_ClassMethods_module
-    assert !Foo.respond_to?(:will_be_orphaned)
-    assert Foo.respond_to?(:hacked_on)
-    assert Foo.respond_to?(:nicer_dsl)
-    assert Foo.respond_to?(:doesnt_clobber)
+    assert_not_respond_to Foo, :will_be_orphaned
+    assert_respond_to Foo, :hacked_on
+    assert_respond_to Foo, :nicer_dsl
+    assert_respond_to Foo, :doesnt_clobber
 
     # Orphan in Foo::ClassMethods, not Bar::ClassMethods.
     assert Foo.const_defined?(:ClassMethods)
diff --git a/activesupport/test/core_ext/module/reachable_test.rb b/activesupport/test/core_ext/module/reachable_test.rb
index 097a72fa5b..f356d46957 100644
--- a/activesupport/test/core_ext/module/reachable_test.rb
+++ b/activesupport/test/core_ext/module/reachable_test.rb
@@ -6,15 +6,15 @@ require "active_support/core_ext/module/reachable"
 class AnonymousTest < ActiveSupport::TestCase
   test "an anonymous class or module is not reachable" do
     assert_deprecated do
-      assert !Module.new.reachable?
-      assert !Class.new.reachable?
+      assert_not_predicate Module.new, :reachable?
+      assert_not_predicate Class.new, :reachable?
     end
   end
 
   test "ordinary named classes or modules are reachable" do
     assert_deprecated do
-      assert Kernel.reachable?
-      assert Object.reachable?
+      assert_predicate Kernel, :reachable?
+      assert_predicate Object, :reachable?
     end
   end
 
@@ -26,8 +26,8 @@ class AnonymousTest < ActiveSupport::TestCase
     self.class.send(:remove_const, :M)
 
     assert_deprecated do
-      assert !c.reachable?
-      assert !m.reachable?
+      assert_not_predicate c, :reachable?
+      assert_not_predicate m, :reachable?
     end
   end
 
@@ -42,10 +42,10 @@ class AnonymousTest < ActiveSupport::TestCase
     eval "module M; end"
 
     assert_deprecated do
-      assert C.reachable?
-      assert M.reachable?
-      assert !c.reachable?
-      assert !m.reachable?
+      assert_predicate C, :reachable?
+      assert_predicate M, :reachable?
+      assert_not_predicate c, :reachable?
+      assert_not_predicate m, :reachable?
     end
   end
 end
diff --git a/activesupport/test/core_ext/module/remove_method_test.rb b/activesupport/test/core_ext/module/remove_method_test.rb
index 8493be8d08..a18fc0a5e4 100644
--- a/activesupport/test/core_ext/module/remove_method_test.rb
+++ b/activesupport/test/core_ext/module/remove_method_test.rb
@@ -32,14 +32,14 @@ class RemoveMethodTest < ActiveSupport::TestCase
     RemoveMethodTests::A.class_eval {
       remove_possible_method(:do_something)
     }
-    assert !RemoveMethodTests::A.new.respond_to?(:do_something)
+    assert_not_respond_to RemoveMethodTests::A.new, :do_something
   end
 
   def test_remove_singleton_method_from_an_object
     RemoveMethodTests::A.class_eval {
       remove_possible_singleton_method(:do_something_else)
     }
-    assert !RemoveMethodTests::A.respond_to?(:do_something_else)
+    assert_not_respond_to RemoveMethodTests::A, :do_something_else
   end
 
   def test_redefine_method_in_an_object
diff --git a/activesupport/test/core_ext/module_test.rb b/activesupport/test/core_ext/module_test.rb
index e918823074..ebbe9c304c 100644
--- a/activesupport/test/core_ext/module_test.rb
+++ b/activesupport/test/core_ext/module_test.rb
@@ -347,7 +347,7 @@ class ModuleTest < ActiveSupport::TestCase
 
   def test_delegation_with_method_arguments
     has_block = HasBlock.new(Block.new)
-    assert has_block.hello?
+    assert_predicate has_block, :hello?
   end
 
   def test_delegate_missing_to_with_method
@@ -383,9 +383,9 @@ class ModuleTest < ActiveSupport::TestCase
   end
 
   def test_delegate_missing_to_affects_respond_to
-    assert DecoratedTester.new(@david).respond_to?(:name)
-    assert_not DecoratedTester.new(@david).respond_to?(:private_name)
-    assert_not DecoratedTester.new(@david).respond_to?(:my_fake_method)
+    assert_respond_to DecoratedTester.new(@david), :name
+    assert_not_respond_to DecoratedTester.new(@david), :private_name
+    assert_not_respond_to DecoratedTester.new(@david), :my_fake_method
 
     assert DecoratedTester.new(@david).respond_to?(:name, true)
     assert_not DecoratedTester.new(@david).respond_to?(:private_name, true)
@@ -414,8 +414,8 @@ class ModuleTest < ActiveSupport::TestCase
 
     place = location.new(Somewhere.new("Such street", "Sad city"))
 
-    assert_not place.respond_to?(:street)
-    assert_not place.respond_to?(:city)
+    assert_not_respond_to place, :street
+    assert_not_respond_to place, :city
 
     assert place.respond_to?(:street, true) # Asking for private method
     assert place.respond_to?(:city, true)
@@ -432,12 +432,12 @@ class ModuleTest < ActiveSupport::TestCase
 
     place = location.new(Somewhere.new("Such street", "Sad city"))
 
-    assert_not place.respond_to?(:street)
-    assert_not place.respond_to?(:city)
+    assert_not_respond_to place, :street
+    assert_not_respond_to place, :city
 
-    assert_not place.respond_to?(:the_street)
+    assert_not_respond_to place, :the_street
     assert place.respond_to?(:the_street, true)
-    assert_not place.respond_to?(:the_city)
+    assert_not_respond_to place, :the_city
     assert place.respond_to?(:the_city, true)
   end
 end
diff --git a/activesupport/test/core_ext/object/duplicable_test.rb b/activesupport/test/core_ext/object/duplicable_test.rb
index b984becce3..635dd7f281 100644
--- a/activesupport/test/core_ext/object/duplicable_test.rb
+++ b/activesupport/test/core_ext/object/duplicable_test.rb
@@ -9,15 +9,9 @@ class DuplicableTest < ActiveSupport::TestCase
   if RUBY_VERSION >= "2.5.0"
     RAISE_DUP = [method(:puts)]
     ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3, Complex(1), Rational(1)]
-  elsif RUBY_VERSION >= "2.4.1"
+  else
     RAISE_DUP = [method(:puts), Complex(1), Rational(1)]
     ALLOW_DUP = ["1", "symbol_from_string".to_sym, Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3]
-  elsif RUBY_VERSION >= "2.4.0"  # Due to 2.4.0 bug. This elsif cannot be removed unless we drop 2.4.0 support...
-    RAISE_DUP = [method(:puts), Complex(1), Rational(1), "symbol_from_string".to_sym]
-    ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56"), nil, false, true, 1, 2.3]
-  else
-    RAISE_DUP = [nil, false, true, :symbol, 1, 2.3, method(:puts), Complex(1), Rational(1)]
-    ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal("4.56")]
   end
 
   def test_duplicable
diff --git a/activesupport/test/core_ext/object/try_test.rb b/activesupport/test/core_ext/object/try_test.rb
index fe68b24bf5..40d6cdd28e 100644
--- a/activesupport/test/core_ext/object/try_test.rb
+++ b/activesupport/test/core_ext/object/try_test.rb
@@ -10,25 +10,25 @@ class ObjectTryTest < ActiveSupport::TestCase
 
   def test_nonexisting_method
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_nil @string.try(method)
   end
 
   def test_nonexisting_method_with_arguments
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_nil @string.try(method, "llo", "y")
   end
 
   def test_nonexisting_method_bang
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_raise(NoMethodError) { @string.try!(method) }
   end
 
   def test_nonexisting_method_with_arguments_bang
     method = :undefined_method
-    assert !@string.respond_to?(method)
+    assert_not_respond_to @string, method
     assert_raise(NoMethodError) { @string.try!(method, "llo", "y") }
   end
 
diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index 5c5abe9fd1..ccaa5dc786 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -9,9 +9,9 @@ require "constantize_test_cases"
 require "active_support/inflector"
 require "active_support/core_ext/string"
 require "active_support/time"
-require "active_support/core_ext/string/strip"
 require "active_support/core_ext/string/output_safety"
 require "active_support/core_ext/string/indent"
+require "active_support/core_ext/string/strip"
 require "time_zone_test_helpers"
 require "yaml"
 
@@ -24,6 +24,10 @@ class StringInflectionsTest < ActiveSupport::TestCase
     assert_equal "", "".strip_heredoc
   end
 
+  def test_strip_heredoc_on_a_frozen_string
+    assert "".freeze.strip_heredoc.frozen?
+  end
+
   def test_strip_heredoc_on_a_string_with_no_lines
     assert_equal "x", "x".strip_heredoc
     assert_equal "x", "    x".strip_heredoc
@@ -259,8 +263,8 @@ class StringInflectionsTest < ActiveSupport::TestCase
   end
 
   def test_string_inquiry
-    assert "production".inquiry.production?
-    assert !"production".inquiry.development?
+    assert_predicate "production".inquiry, :production?
+    assert_not_predicate "production".inquiry, :development?
   end
 
   def test_truncate
@@ -281,6 +285,68 @@ class StringInflectionsTest < ActiveSupport::TestCase
     assert_equal "Hello Big[...]", "Hello Big World!".truncate(15, omission: "[...]", separator: /\s/)
   end
 
+  def test_truncate_bytes
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: nil)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: " ")
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: "🖖")
+
+    assert_equal "👍👍👍…", "👍👍👍👍".truncate_bytes(15)
+    assert_equal "👍👍👍", "👍👍👍👍".truncate_bytes(15, omission: nil)
+    assert_equal "👍👍👍 ", "👍👍👍👍".truncate_bytes(15, omission: " ")
+    assert_equal "👍👍🖖", "👍👍👍👍".truncate_bytes(15, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(5)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(5, omission: nil)
+    assert_equal "👍 ", "👍👍👍👍".truncate_bytes(5, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(5, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(4)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(4, omission: nil)
+    assert_equal " ", "👍👍👍👍".truncate_bytes(4, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(4, omission: "🖖")
+
+    assert_raise ArgumentError do
+      "👍👍👍👍".truncate_bytes(3, omission: "🖖")
+    end
+  end
+
+  def test_truncate_bytes_preserves_codepoints
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: nil)
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: " ")
+    assert_equal "👍👍👍👍", "👍👍👍👍".truncate_bytes(16, omission: "🖖")
+
+    assert_equal "👍👍👍…", "👍👍👍👍".truncate_bytes(15)
+    assert_equal "👍👍👍", "👍👍👍👍".truncate_bytes(15, omission: nil)
+    assert_equal "👍👍👍 ", "👍👍👍👍".truncate_bytes(15, omission: " ")
+    assert_equal "👍👍🖖", "👍👍👍👍".truncate_bytes(15, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(5)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(5, omission: nil)
+    assert_equal "👍 ", "👍👍👍👍".truncate_bytes(5, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(5, omission: "🖖")
+
+    assert_equal "…", "👍👍👍👍".truncate_bytes(4)
+    assert_equal "👍", "👍👍👍👍".truncate_bytes(4, omission: nil)
+    assert_equal " ", "👍👍👍👍".truncate_bytes(4, omission: " ")
+    assert_equal "🖖", "👍👍👍👍".truncate_bytes(4, omission: "🖖")
+
+    assert_raise ArgumentError do
+      "👍👍👍👍".truncate_bytes(3, omission: "🖖")
+    end
+  end
+
+  def test_truncates_bytes_preserves_grapheme_clusters
+    assert_equal "a ", "a ❤️ b".truncate_bytes(2, omission: nil)
+    assert_equal "a ", "a ❤️ b".truncate_bytes(3, omission: nil)
+    assert_equal "a ", "a ❤️ b".truncate_bytes(7, omission: nil)
+    assert_equal "a ❤️", "a ❤️ b".truncate_bytes(8, omission: nil)
+
+    assert_equal "a ", "a 👩‍❤️‍👩".truncate_bytes(13, omission: nil)
+    assert_equal "", "👩‍❤️‍👩".truncate_bytes(13, omission: nil)
+  end
+
   def test_truncate_words
     assert_equal "Hello Big World!", "Hello Big World!".truncate_words(3)
     assert_equal "Hello Big...", "Hello Big World!".truncate_words(2)
@@ -317,7 +383,7 @@ class StringInflectionsTest < ActiveSupport::TestCase
   end
 
   def test_truncate_should_not_be_html_safe
-    assert !"Hello World!".truncate(12).html_safe?
+    assert_not_predicate "Hello World!".truncate(12), :html_safe?
   end
 
   def test_remove
@@ -639,7 +705,7 @@ end
 
 class StringBehaviourTest < ActiveSupport::TestCase
   def test_acts_like_string
-    assert "Bambi".acts_like_string?
+    assert_predicate "Bambi", :acts_like_string?
   end
 end
 
@@ -654,10 +720,10 @@ class CoreExtStringMultibyteTest < ActiveSupport::TestCase
   end
 
   def test_string_should_recognize_utf8_strings
-    assert UTF8_STRING.is_utf8?
-    assert ASCII_STRING.is_utf8?
-    assert !EUC_JP_STRING.is_utf8?
-    assert !INVALID_UTF8_STRING.is_utf8?
+    assert_predicate UTF8_STRING, :is_utf8?
+    assert_predicate ASCII_STRING, :is_utf8?
+    assert_not_predicate EUC_JP_STRING, :is_utf8?
+    assert_not_predicate INVALID_UTF8_STRING, :is_utf8?
   end
 
   def test_mb_chars_returns_instance_of_proxy_class
@@ -676,12 +742,12 @@ class OutputSafetyTest < ActiveSupport::TestCase
   end
 
   test "A string is unsafe by default" do
-    assert !@string.html_safe?
+    assert_not_predicate @string, :html_safe?
   end
 
   test "A string can be marked safe" do
     string = @string.html_safe
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Marking a string safe returns the string" do
@@ -689,15 +755,15 @@ class OutputSafetyTest < ActiveSupport::TestCase
   end
 
   test "An integer is safe by default" do
-    assert 5.html_safe?
+    assert_predicate 5, :html_safe?
   end
 
   test "a float is safe by default" do
-    assert 5.7.html_safe?
+    assert_predicate 5.7, :html_safe?
   end
 
   test "An object is unsafe by default" do
-    assert !@object.html_safe?
+    assert_not_predicate @object, :html_safe?
   end
 
   test "Adding an object to a safe string returns a safe string" do
@@ -705,7 +771,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string << @object
 
     assert_equal "helloother", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Adding a safe string to another safe string returns a safe string" do
@@ -714,7 +780,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     @combination = @other_string + string
 
     assert_equal "otherhello", @combination
-    assert @combination.html_safe?
+    assert_predicate @combination, :html_safe?
   end
 
   test "Adding an unsafe string to a safe string escapes it and returns a safe string" do
@@ -725,20 +791,20 @@ class OutputSafetyTest < ActiveSupport::TestCase
     assert_equal "other&lt;foo&gt;", @combination
     assert_equal "hello<foo>", @other_combination
 
-    assert @combination.html_safe?
-    assert !@other_combination.html_safe?
+    assert_predicate @combination, :html_safe?
+    assert_not_predicate @other_combination, :html_safe?
   end
 
   test "Prepending safe onto unsafe yields unsafe" do
     @string.prepend "other".html_safe
-    assert !@string.html_safe?
+    assert_not_predicate @string, :html_safe?
     assert_equal "otherhello", @string
   end
 
   test "Prepending unsafe onto safe yields escaped safe" do
     other = "other".html_safe
     other.prepend "<foo>"
-    assert other.html_safe?
+    assert_predicate other, :html_safe?
     assert_equal "&lt;foo&gt;other", other
   end
 
@@ -747,14 +813,14 @@ class OutputSafetyTest < ActiveSupport::TestCase
 
     string = @string.html_safe
     @other_string.concat(string)
-    assert !@other_string.html_safe?
+    assert_not_predicate @other_string, :html_safe?
   end
 
   test "Concatting unsafe onto safe yields escaped safe" do
     @other_string = "other".html_safe
     string = @other_string.concat("<foo>")
     assert_equal "other&lt;foo&gt;", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Concatting safe onto safe yields safe" do
@@ -762,7 +828,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string.concat(string)
-    assert @other_string.html_safe?
+    assert_predicate @other_string, :html_safe?
   end
 
   test "Concatting safe onto unsafe with << yields unsafe" do
@@ -770,14 +836,14 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string << string
-    assert !@other_string.html_safe?
+    assert_not_predicate @other_string, :html_safe?
   end
 
   test "Concatting unsafe onto safe with << yields escaped safe" do
     @other_string = "other".html_safe
     string = @other_string << "<foo>"
     assert_equal "other&lt;foo&gt;", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Concatting safe onto safe with << yields safe" do
@@ -785,7 +851,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string << string
-    assert @other_string.html_safe?
+    assert_predicate @other_string, :html_safe?
   end
 
   test "Concatting safe onto unsafe with % yields unsafe" do
@@ -793,7 +859,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string = @other_string % string
-    assert !@other_string.html_safe?
+    assert_not_predicate @other_string, :html_safe?
   end
 
   test "Concatting unsafe onto safe with % yields escaped safe" do
@@ -801,7 +867,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @other_string % "<foo>"
 
     assert_equal "other&lt;foo&gt;", string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "Concatting safe onto safe with % yields safe" do
@@ -809,7 +875,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
 
     @other_string = @other_string % string
-    assert @other_string.html_safe?
+    assert_predicate @other_string, :html_safe?
   end
 
   test "Concatting with % doesn't modify a string" do
@@ -823,7 +889,7 @@ class OutputSafetyTest < ActiveSupport::TestCase
     string = @string.html_safe
     string = string.concat(13)
     assert_equal "hello".dup.concat(13), string
-    assert string.html_safe?
+    assert_predicate string, :html_safe?
   end
 
   test "emits normal string yaml" do
@@ -832,8 +898,8 @@ class OutputSafetyTest < ActiveSupport::TestCase
 
   test "call to_param returns a normal string" do
     string = @string.html_safe
-    assert string.html_safe?
-    assert !string.to_param.html_safe?
+    assert_predicate string, :html_safe?
+    assert_not_predicate string.to_param, :html_safe?
   end
 
   test "ERB::Util.html_escape should escape unsafe characters" do
diff --git a/activesupport/test/core_ext/time_ext_test.rb b/activesupport/test/core_ext/time_ext_test.rb
index 01cf1938be..e1cb22fda8 100644
--- a/activesupport/test/core_ext/time_ext_test.rb
+++ b/activesupport/test/core_ext/time_ext_test.rb
@@ -737,7 +737,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_time
-    assert Time.new.acts_like_time?
+    assert_predicate Time.new, :acts_like_time?
   end
 
   def test_formatted_offset_with_utc
@@ -756,26 +756,26 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_compare_with_time
-    assert_equal  1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999)
-    assert_equal  0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999)
+    assert_equal 0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0, 001))
   end
 
   def test_compare_with_datetime
-    assert_equal  1, Time.utc(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, Time.utc(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, Time.utc(2000) <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, Time.utc(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, Time.utc(2000) <=> DateTime.civil(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_time_with_zone
-    assert_equal  1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
-    assert_equal  0, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
+    assert_equal 1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
+    assert_equal 0, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
     assert_equal(-1, Time.utc(2000) <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone["UTC"]))
   end
 
   def test_compare_with_string
-    assert_equal   1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999).to_s
-    assert_equal   0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
+    assert_equal 1, Time.utc(2000) <=> Time.utc(1999, 12, 31, 23, 59, 59, 999).to_s
+    assert_equal 0, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 0).to_s
     assert_equal(-1, Time.utc(2000) <=> Time.utc(2000, 1, 1, 0, 0, 1, 0).to_s)
     assert_nil Time.utc(2000) <=> "Invalid as Time"
   end
@@ -863,11 +863,11 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
   end
 
   def test_minus_with_time_with_zone
-    assert_equal  86_400.0, Time.utc(2000, 1, 2) - ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1), ActiveSupport::TimeZone["UTC"])
+    assert_equal 86_400.0, Time.utc(2000, 1, 2) - ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1), ActiveSupport::TimeZone["UTC"])
   end
 
   def test_minus_with_datetime
-    assert_equal  86_400.0, Time.utc(2000, 1, 2) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_400.0, Time.utc(2000, 1, 2) - DateTime.civil(2000, 1, 1)
   end
 
   def test_time_created_with_local_constructor_cannot_represent_times_during_hour_skipped_by_dst
@@ -875,7 +875,7 @@ class TimeExtCalculationsTest < ActiveSupport::TestCase
       # On Apr 2 2006 at 2:00AM in US, clocks were moved forward to 3:00AM.
       # Therefore, 2AM EST doesn't exist for this date; Time.local fails over to 3:00AM EDT
       assert_equal Time.local(2006, 4, 2, 3), Time.local(2006, 4, 2, 2)
-      assert Time.local(2006, 4, 2, 2).dst?
+      assert_predicate Time.local(2006, 4, 2, 2), :dst?
     end
   end
 
diff --git a/activesupport/test/core_ext/time_with_zone_test.rb b/activesupport/test/core_ext/time_with_zone_test.rb
index b25747eadb..2ea5f0921c 100644
--- a/activesupport/test/core_ext/time_with_zone_test.rb
+++ b/activesupport/test/core_ext/time_with_zone_test.rb
@@ -3,7 +3,6 @@
 require "abstract_unit"
 require "active_support/time"
 require "time_zone_test_helpers"
-require "active_support/core_ext/string/strip"
 require "yaml"
 
 class TimeWithZoneTest < ActiveSupport::TestCase
@@ -163,7 +162,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_to_yaml
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       --- !ruby/object:ActiveSupport::TimeWithZone
       utc: 2000-01-01 00:00:00.000000000 Z
       zone: !ruby/object:ActiveSupport::TimeZone
@@ -175,7 +174,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_ruby_to_yaml
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       ---
       twz: !ruby/object:ActiveSupport::TimeWithZone
         utc: 2000-01-01 00:00:00.000000000 Z
@@ -188,7 +187,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_yaml_load
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       --- !ruby/object:ActiveSupport::TimeWithZone
       utc: 2000-01-01 00:00:00.000000000 Z
       zone: !ruby/object:ActiveSupport::TimeZone
@@ -200,7 +199,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_ruby_yaml_load
-    yaml = <<-EOF.strip_heredoc
+    yaml = <<~EOF
       ---
       twz: !ruby/object:ActiveSupport::TimeWithZone
         utc: 2000-01-01 00:00:00.000000000 Z
@@ -221,20 +220,20 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_compare_with_time
-    assert_equal  1, @twz <=> Time.utc(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, @twz <=> Time.utc(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, @twz <=> Time.utc(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, @twz <=> Time.utc(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, @twz <=> Time.utc(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_datetime
-    assert_equal  1, @twz <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
-    assert_equal  0, @twz <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
+    assert_equal 1, @twz <=> DateTime.civil(1999, 12, 31, 23, 59, 59)
+    assert_equal 0, @twz <=> DateTime.civil(2000, 1, 1, 0, 0, 0)
     assert_equal(-1, @twz <=> DateTime.civil(2000, 1, 1, 0, 0, 1))
   end
 
   def test_compare_with_time_with_zone
-    assert_equal  1, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
-    assert_equal  0, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
+    assert_equal 1, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(1999, 12, 31, 23, 59, 59), ActiveSupport::TimeZone["UTC"])
+    assert_equal 0, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0), ActiveSupport::TimeZone["UTC"])
     assert_equal(-1, @twz <=> ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 1), ActiveSupport::TimeZone["UTC"]))
   end
 
@@ -340,13 +339,13 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_minus_with_time
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 1)
   end
 
   def test_minus_with_time_precision
-    assert_equal  86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
-    assert_equal  86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
+    assert_equal 86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
+    assert_equal 86_399.999999998,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["Hawaii"]) - Time.utc(2000, 1, 2, 0, 0, 0, Rational(1, 1000))
   end
 
   def test_minus_with_time_with_zone
@@ -358,20 +357,20 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   def test_minus_with_time_with_zone_precision
     twz1 = ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 0, 0, 0, Rational(1, 1000)), ActiveSupport::TimeZone["UTC"])
     twz2 = ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"])
-    assert_equal  86_399.999999998,  twz2 - twz1
+    assert_equal 86_399.999999998,  twz2 - twz1
   end
 
   def test_minus_with_datetime
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
   end
 
   def test_minus_with_datetime_precision
-    assert_equal  86_399.999999999,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_399.999999999,  ActiveSupport::TimeWithZone.new(Time.utc(2000, 1, 1, 23, 59, 59, Rational(999999999, 1000)), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
   end
 
   def test_minus_with_wrapped_datetime
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
-    assert_equal  86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - Time.utc(2000, 1, 1)
+    assert_equal 86_400.0,  ActiveSupport::TimeWithZone.new(DateTime.civil(2000, 1, 2), ActiveSupport::TimeZone["UTC"]) - DateTime.civil(2000, 1, 1)
   end
 
   def test_plus_and_minus_enforce_spring_dst_rules
@@ -481,7 +480,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_time
-    assert @twz.acts_like_time?
+    assert_predicate @twz, :acts_like_time?
     assert @twz.acts_like?(:time)
     assert ActiveSupport::TimeWithZone.new(DateTime.civil(2000), @time_zone).acts_like?(:time)
   end
@@ -492,7 +491,7 @@ class TimeWithZoneTest < ActiveSupport::TestCase
   end
 
   def test_blank?
-    assert_not @twz.blank?
+    assert_not_predicate @twz, :blank?
   end
 
   def test_is_a
@@ -514,10 +513,10 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     marshal_str = Marshal.dump(@twz)
     mtime = Marshal.load(marshal_str)
     assert_equal Time.utc(2000, 1, 1, 0), mtime.utc
-    assert mtime.utc.utc?
+    assert_predicate mtime.utc, :utc?
     assert_equal ActiveSupport::TimeZone["Eastern Time (US & Canada)"], mtime.time_zone
     assert_equal Time.utc(1999, 12, 31, 19), mtime.time
-    assert mtime.time.utc?
+    assert_predicate mtime.time, :utc?
     assert_equal @twz.inspect, mtime.inspect
   end
 
@@ -526,16 +525,16 @@ class TimeWithZoneTest < ActiveSupport::TestCase
     marshal_str = Marshal.dump(twz)
     mtime = Marshal.load(marshal_str)
     assert_equal Time.utc(2000, 1, 1, 0), mtime.utc
-    assert mtime.utc.utc?
+    assert_predicate mtime.utc, :utc?
     assert_equal "America/New_York", mtime.time_zone.name
     assert_equal Time.utc(1999, 12, 31, 19), mtime.time
-    assert mtime.time.utc?
+    assert_predicate mtime.time, :utc?
     assert_equal @twz.inspect, mtime.inspect
   end
 
   def test_freeze
     @twz.freeze
-    assert @twz.frozen?
+    assert_predicate @twz, :frozen?
   end
 
   def test_freeze_preloads_instance_variables
@@ -1035,8 +1034,8 @@ class TimeWithZoneMethodsForTimeAndDateTimeTest < ActiveSupport::TestCase
 
   def test_nil_time_zone
     Time.use_zone nil do
-      assert !@t.in_time_zone.respond_to?(:period), "no period method"
-      assert !@dt.in_time_zone.respond_to?(:period), "no period method"
+      assert_not_respond_to @t.in_time_zone, :period, "no period method"
+      assert_not_respond_to @dt.in_time_zone, :period, "no period method"
     end
   end
 
@@ -1224,7 +1223,7 @@ class TimeWithZoneMethodsForDate < ActiveSupport::TestCase
 
   def test_nil_time_zone
     with_tz_default nil do
-      assert !@d.in_time_zone.respond_to?(:period), "no period method"
+      assert_not_respond_to @d.in_time_zone, :period, "no period method"
     end
   end
 
@@ -1273,9 +1272,9 @@ class TimeWithZoneMethodsForString < ActiveSupport::TestCase
 
   def test_nil_time_zone
     with_tz_default nil do
-      assert !@s.in_time_zone.respond_to?(:period), "no period method"
-      assert !@u.in_time_zone.respond_to?(:period), "no period method"
-      assert !@z.in_time_zone.respond_to?(:period), "no period method"
+      assert_not_respond_to @s.in_time_zone, :period, "no period method"
+      assert_not_respond_to @u.in_time_zone, :period, "no period method"
+      assert_not_respond_to @z.in_time_zone, :period, "no period method"
     end
   end
 
diff --git a/activesupport/test/dependencies_test.rb b/activesupport/test/dependencies_test.rb
index d636da46d2..c0c4c4cac5 100644
--- a/activesupport/test/dependencies_test.rb
+++ b/activesupport/test/dependencies_test.rb
@@ -185,6 +185,61 @@ class DependenciesTest < ActiveSupport::TestCase
     end
   end
 
+  # Regression see https://github.com/rails/rails/issues/31694
+  def test_included_constant_that_changes_to_have_exception_then_back_does_not_loop_forever
+    # This constant references a nested constant whose namespace will be auto-generated
+    parent_constant = <<-RUBY
+      class ConstantReloadError
+        AnotherConstant::ReloadError
+      end
+    RUBY
+
+    # This constant's namespace will be auto-generated,
+    # also, we'll edit it to contain an error at load-time
+    child_constant = <<-RUBY
+      class AnotherConstant::ReloadError
+        # no_such_method_as_this
+      end
+    RUBY
+
+    # Create a version which contains an error during loading
+    child_constant_with_error = child_constant.sub("# no_such_method_as_this", "no_such_method_as_this")
+
+    fixtures_path = File.join(__dir__, "autoloading_fixtures")
+    Dir.mktmpdir(nil, fixtures_path) do |tmpdir|
+      # Set up the file structure where constants will be loaded from
+      child_constant_path = "#{tmpdir}/another_constant/reload_error.rb"
+      File.write("#{tmpdir}/constant_reload_error.rb", parent_constant)
+      Dir.mkdir("#{tmpdir}/another_constant")
+      File.write(child_constant_path, child_constant_with_error)
+
+      tmpdir_name = tmpdir.split("/").last
+      with_loading("autoloading_fixtures/#{tmpdir_name}") do
+        # Load the file, with the error:
+        assert_raises(NameError) {
+          ConstantReloadError
+        }
+
+        Timeout.timeout(0.1) do
+          # Remove the constant, as if Rails development middleware is reloading changed files:
+          ActiveSupport::Dependencies.remove_unloadable_constants!
+          refute defined?(AnotherConstant::ReloadError)
+        end
+
+        # Change the file, so that it is **correct** this time:
+        File.write(child_constant_path, child_constant)
+
+        # Again: Remove the constant, as if Rails development middleware is reloading changed files:
+        ActiveSupport::Dependencies.remove_unloadable_constants!
+        refute defined?(AnotherConstant::ReloadError)
+
+        # Now, reload the _fixed_ constant:
+        assert ConstantReloadError
+        assert AnotherConstant::ReloadError
+      end
+    end
+  end
+
   def test_module_loading
     with_autoloading_fixtures do
       assert_kind_of Module, A
@@ -752,7 +807,7 @@ class DependenciesTest < ActiveSupport::TestCase
     Object.const_set :C, Class.new { def self.before_remove_const; end }
     C.unloadable
     assert_called(C, :before_remove_const, times: 1) do
-      assert C.respond_to?(:before_remove_const)
+      assert_respond_to C, :before_remove_const
       ActiveSupport::Dependencies.clear
       assert !defined?(C)
     end
diff --git a/activesupport/test/deprecation_test.rb b/activesupport/test/deprecation_test.rb
index f2267a822f..60673c032b 100644
--- a/activesupport/test/deprecation_test.rb
+++ b/activesupport/test/deprecation_test.rb
@@ -158,7 +158,7 @@ class DeprecationTest < ActiveSupport::TestCase
     stderr_output = capture(:stderr) {
       assert_nil behavior.call("Some error!", ["call stack!"], "horizon", "gem")
     }
-    assert stderr_output.empty?
+    assert_empty stderr_output
   end
 
   def test_default_notify_behavior
diff --git a/activesupport/test/descendants_tracker_test_cases.rb b/activesupport/test/descendants_tracker_test_cases.rb
index 1f8b4a8605..2c94c3c56c 100644
--- a/activesupport/test/descendants_tracker_test_cases.rb
+++ b/activesupport/test/descendants_tracker_test_cases.rb
@@ -37,7 +37,7 @@ module DescendantsTrackerTestCases
     mark_as_autoloaded(*ALL) do
       ActiveSupport::DescendantsTracker.clear
       ALL.each do |k|
-        assert ActiveSupport::DescendantsTracker.descendants(k).empty?
+        assert_empty ActiveSupport::DescendantsTracker.descendants(k)
       end
     end
   end
diff --git a/activesupport/test/descendants_tracker_with_autoloading_test.rb b/activesupport/test/descendants_tracker_with_autoloading_test.rb
index 7c396b7c8e..d4fedb5a67 100644
--- a/activesupport/test/descendants_tracker_with_autoloading_test.rb
+++ b/activesupport/test/descendants_tracker_with_autoloading_test.rb
@@ -12,7 +12,7 @@ class DescendantsTrackerWithAutoloadingTest < ActiveSupport::TestCase
     mark_as_autoloaded(*ALL) do
       ActiveSupport::DescendantsTracker.clear
       ALL.each do |k|
-        assert ActiveSupport::DescendantsTracker.descendants(k).empty?
+        assert_empty ActiveSupport::DescendantsTracker.descendants(k)
       end
     end
   end
diff --git a/activesupport/test/evented_file_update_checker_test.rb b/activesupport/test/evented_file_update_checker_test.rb
index 9b560f7f42..d3af0dbef3 100644
--- a/activesupport/test/evented_file_update_checker_test.rb
+++ b/activesupport/test/evented_file_update_checker_test.rb
@@ -39,18 +39,18 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
     FileUtils.touch(tmpfiles)
 
     checker = new_checker(tmpfiles) {}
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     # Pipes used for flow control across fork.
     boot_reader,  boot_writer  = IO.pipe
     touch_reader, touch_writer = IO.pipe
 
     pid = fork do
-      assert checker.updated?
+      assert_predicate checker, :updated?
 
       # Clear previous check value.
       checker.execute
-      assert !checker.updated?
+      assert_not_predicate checker, :updated?
 
       # Fork is booted, ready for file to be touched
       # notify parent process.
@@ -60,7 +60,7 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
       # has been touched.
       IO.select([touch_reader])
 
-      assert checker.updated?
+      assert_predicate checker, :updated?
     end
 
     assert pid
@@ -72,7 +72,7 @@ class EventedFileUpdateCheckerTest < ActiveSupport::TestCase
     # Notify fork that files have been touched.
     touch_writer.write("touched")
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
 
     Process.wait(pid)
   end
diff --git a/activesupport/test/file_update_checker_shared_tests.rb b/activesupport/test/file_update_checker_shared_tests.rb
index f8266dac06..daf7f9d139 100644
--- a/activesupport/test/file_update_checker_shared_tests.rb
+++ b/activesupport/test/file_update_checker_shared_tests.rb
@@ -89,12 +89,12 @@ module FileUpdateCheckerSharedTests
     i = 0
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     touch(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
   end
 
   test "updated should become true when watched files are modified" do
@@ -103,12 +103,12 @@ module FileUpdateCheckerSharedTests
     FileUtils.touch(tmpfiles)
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     touch(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
   end
 
   test "updated should become true when watched files are deleted" do
@@ -117,12 +117,12 @@ module FileUpdateCheckerSharedTests
     FileUtils.touch(tmpfiles)
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     rm_f(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
   end
 
   test "should be robust to handle files with wrong modified time" do
@@ -164,14 +164,14 @@ module FileUpdateCheckerSharedTests
     i = 0
 
     checker = new_checker(tmpfiles) { i += 1 }
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
 
     touch(tmpfiles)
     wait
 
-    assert checker.updated?
+    assert_predicate checker, :updated?
     checker.execute
-    assert !checker.updated?
+    assert_not_predicate checker, :updated?
   end
 
   test "should execute the block if files change in a watched directory one extension" do
diff --git a/activesupport/test/hash_with_indifferent_access_test.rb b/activesupport/test/hash_with_indifferent_access_test.rb
index 41d653fa59..b06250baf8 100644
--- a/activesupport/test/hash_with_indifferent_access_test.rb
+++ b/activesupport/test/hash_with_indifferent_access_test.rb
@@ -169,8 +169,6 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
   end
 
   def test_indifferent_fetch_values
-    skip unless Hash.method_defined?(:fetch_values)
-
     @mixed = @mixed.with_indifferent_access
 
     assert_equal [1, 2], @mixed.fetch_values("a", "b")
@@ -404,6 +402,12 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
 
     assert_equal({ "aa" => 1, "bb" => 2 }, hash)
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
+
+    hash = ActiveSupport::HashWithIndifferentAccess.new(@strings).transform_keys { |k| k.to_sym }
+
+    assert_equal(1, hash[:a])
+    assert_equal(1, hash["a"])
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, hash
   end
 
   def test_indifferent_transform_keys_bang
@@ -412,6 +416,13 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
 
     assert_equal({ "aa" => 1, "bb" => 2 }, indifferent_strings)
     assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
+
+    indifferent_strings = ActiveSupport::HashWithIndifferentAccess.new(@strings)
+    indifferent_strings.transform_keys! { |k| k.to_sym }
+
+    assert_equal(1, indifferent_strings[:a])
+    assert_equal(1, indifferent_strings["a"])
+    assert_instance_of ActiveSupport::HashWithIndifferentAccess, indifferent_strings
   end
 
   def test_indifferent_transform_values
@@ -562,7 +573,6 @@ class HashWithIndifferentAccessTest < ActiveSupport::TestCase
   end
 
   def test_nested_dig_indifferent_access
-    skip if RUBY_VERSION < "2.3.0"
     data = { "this" => { "views" => 1234 } }.with_indifferent_access
     assert_equal 1234, data.dig(:this, :views)
   end
diff --git a/activesupport/test/inflector_test.rb b/activesupport/test/inflector_test.rb
index 0e3e576a70..5e50acf5db 100644
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -460,12 +460,12 @@ class InflectorTest < ActiveSupport::TestCase
 
     ActiveSupport::Inflector.inflections(:es) { |inflect| inflect.clear }
 
-    assert ActiveSupport::Inflector.inflections(:es).plurals.empty?
-    assert ActiveSupport::Inflector.inflections(:es).singulars.empty?
-    assert ActiveSupport::Inflector.inflections(:es).uncountables.empty?
-    assert !ActiveSupport::Inflector.inflections.plurals.empty?
-    assert !ActiveSupport::Inflector.inflections.singulars.empty?
-    assert !ActiveSupport::Inflector.inflections.uncountables.empty?
+    assert_empty ActiveSupport::Inflector.inflections(:es).plurals
+    assert_empty ActiveSupport::Inflector.inflections(:es).singulars
+    assert_empty ActiveSupport::Inflector.inflections(:es).uncountables
+    assert_not_empty ActiveSupport::Inflector.inflections.plurals
+    assert_not_empty ActiveSupport::Inflector.inflections.singulars
+    assert_not_empty ActiveSupport::Inflector.inflections.uncountables
   end
 
   def test_clear_all
@@ -478,10 +478,10 @@ class InflectorTest < ActiveSupport::TestCase
 
       inflect.clear :all
 
-      assert inflect.plurals.empty?
-      assert inflect.singulars.empty?
-      assert inflect.uncountables.empty?
-      assert inflect.humans.empty?
+      assert_empty inflect.plurals
+      assert_empty inflect.singulars
+      assert_empty inflect.uncountables
+      assert_empty inflect.humans
     end
   end
 
@@ -495,10 +495,10 @@ class InflectorTest < ActiveSupport::TestCase
 
       inflect.clear
 
-      assert inflect.plurals.empty?
-      assert inflect.singulars.empty?
-      assert inflect.uncountables.empty?
-      assert inflect.humans.empty?
+      assert_empty inflect.plurals
+      assert_empty inflect.singulars
+      assert_empty inflect.uncountables
+      assert_empty inflect.humans
     end
   end
 
diff --git a/activesupport/test/multibyte_chars_test.rb b/activesupport/test/multibyte_chars_test.rb
index f51fbe2671..560b86b1a3 100644
--- a/activesupport/test/multibyte_chars_test.rb
+++ b/activesupport/test/multibyte_chars_test.rb
@@ -469,10 +469,10 @@ class MultibyteCharsUTF8BehaviourTest < ActiveSupport::TestCase
   end
 
   def test_respond_to_knows_which_methods_the_proxy_responds_to
-    assert "".mb_chars.respond_to?(:slice) # Defined on Chars
-    assert "".mb_chars.respond_to?(:capitalize!) # Defined on Chars
-    assert "".mb_chars.respond_to?(:gsub) # Defined on String
-    assert !"".mb_chars.respond_to?(:undefined_method) # Not defined
+    assert_respond_to "".mb_chars, :slice # Defined on Chars
+    assert_respond_to "".mb_chars, :capitalize! # Defined on Chars
+    assert_respond_to "".mb_chars, :gsub # Defined on String
+    assert_not_respond_to "".mb_chars, :undefined_method # Not defined
   end
 
   def test_method_works_for_proxyed_methods
@@ -485,7 +485,7 @@ class MultibyteCharsUTF8BehaviourTest < ActiveSupport::TestCase
   end
 
   def test_acts_like_string
-    assert "Bambi".mb_chars.acts_like_string?
+    assert_predicate "Bambi".mb_chars, :acts_like_string?
   end
 end
 
diff --git a/activesupport/test/multibyte_unicode_database_test.rb b/activesupport/test/multibyte_unicode_database_test.rb
deleted file mode 100644
index 540a34493d..0000000000
--- a/activesupport/test/multibyte_unicode_database_test.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-# frozen_string_literal: true
-
-require "abstract_unit"
-
-class MultibyteUnicodeDatabaseTest < ActiveSupport::TestCase
-  include ActiveSupport::Multibyte::Unicode
-
-  def setup
-    @ucd = UnicodeDatabase.new
-  end
-
-  UnicodeDatabase::ATTRIBUTES.each do |attribute|
-    define_method "test_lazy_loading_on_attribute_access_of_#{attribute}" do
-      assert_called(@ucd, :load) do
-        @ucd.send(attribute)
-      end
-    end
-  end
-
-  def test_load
-    @ucd.load
-    UnicodeDatabase::ATTRIBUTES.each do |attribute|
-      assert @ucd.send(attribute).length > 1
-    end
-  end
-end
diff --git a/activesupport/test/notifications/instrumenter_test.rb b/activesupport/test/notifications/instrumenter_test.rb
index 1d76c91d30..d5c9e82e9f 100644
--- a/activesupport/test/notifications/instrumenter_test.rb
+++ b/activesupport/test/notifications/instrumenter_test.rb
@@ -47,13 +47,13 @@ module ActiveSupport
       def test_start
         instrumenter.start("foo", payload)
         assert_equal [["foo", instrumenter.id, payload]], notifier.starts
-        assert_predicate notifier.finishes, :empty?
+        assert_empty notifier.finishes
       end
 
       def test_finish
         instrumenter.finish("foo", payload)
         assert_equal [["foo", instrumenter.id, payload]], notifier.finishes
-        assert_predicate notifier.starts, :empty?
+        assert_empty notifier.starts
       end
     end
   end
diff --git a/activesupport/test/notifications_test.rb b/activesupport/test/notifications_test.rb
index 5cfbd60131..28a02aafc8 100644
--- a/activesupport/test/notifications_test.rb
+++ b/activesupport/test/notifications_test.rb
@@ -250,8 +250,8 @@ module Notifications
       time = Time.now
       event = event(:foo, time, time + 0.01, random_id, {})
 
-      assert_equal    :foo, event.name
-      assert_equal    time, event.time
+      assert_equal :foo, event.name
+      assert_equal time, event.time
       assert_in_delta 10.0, event.duration, 0.00001
     end
 
diff --git a/activesupport/test/ordered_options_test.rb b/activesupport/test/ordered_options_test.rb
index 2c67bb02ac..cba5b8a8de 100644
--- a/activesupport/test/ordered_options_test.rb
+++ b/activesupport/test/ordered_options_test.rb
@@ -82,8 +82,8 @@ class OrderedOptionsTest < ActiveSupport::TestCase
 
   def test_introspection
     a = ActiveSupport::OrderedOptions.new
-    assert a.respond_to?(:blah)
-    assert a.respond_to?(:blah=)
+    assert_respond_to a, :blah
+    assert_respond_to a, :blah=
     assert_equal 42, a.method(:blah=).call(42)
     assert_equal 42, a.method(:blah).call
   end
@@ -91,7 +91,7 @@ class OrderedOptionsTest < ActiveSupport::TestCase
   def test_raises_with_bang
     a = ActiveSupport::OrderedOptions.new
     a[:foo] = :bar
-    assert a.respond_to?(:foo!)
+    assert_respond_to a, :foo!
 
     assert_nothing_raised { a.foo! }
     assert_equal a.foo, a.foo!
diff --git a/activesupport/test/safe_buffer_test.rb b/activesupport/test/safe_buffer_test.rb
index 05c2fb59be..1c19c92bb0 100644
--- a/activesupport/test/safe_buffer_test.rb
+++ b/activesupport/test/safe_buffer_test.rb
@@ -39,7 +39,7 @@ class SafeBufferTest < ActiveSupport::TestCase
   end
 
   test "Should be considered safe" do
-    assert @buffer.html_safe?
+    assert_predicate @buffer, :html_safe?
   end
 
   test "Should return a safe buffer when calling to_s" do
@@ -78,13 +78,13 @@ class SafeBufferTest < ActiveSupport::TestCase
   test "Should not return safe buffer from gsub" do
     altered_buffer = @buffer.gsub("", "asdf")
     assert_equal "asdf", altered_buffer
-    assert !altered_buffer.html_safe?
+    assert_not_predicate altered_buffer, :html_safe?
   end
 
   test "Should not return safe buffer from gsub!" do
     @buffer.gsub!("", "asdf")
     assert_equal "asdf", @buffer
-    assert !@buffer.html_safe?
+    assert_not_predicate @buffer, :html_safe?
   end
 
   test "Should escape dirty buffers on add" do
@@ -101,13 +101,13 @@ class SafeBufferTest < ActiveSupport::TestCase
 
   test "Should preserve html_safe? status on copy" do
     @buffer.gsub!("", "<>")
-    assert !@buffer.dup.html_safe?
+    assert_not_predicate @buffer.dup, :html_safe?
   end
 
   test "Should return safe buffer when added with another safe buffer" do
     clean = "<script>".html_safe
     result_buffer = @buffer + clean
-    assert result_buffer.html_safe?
+    assert_predicate result_buffer, :html_safe?
     assert_equal "<script>", result_buffer
   end
 
@@ -127,8 +127,8 @@ class SafeBufferTest < ActiveSupport::TestCase
   end
 
   test "clone_empty keeps the original dirtyness" do
-    assert @buffer.clone_empty.html_safe?
-    assert !@buffer.gsub!("", "").clone_empty.html_safe?
+    assert_predicate @buffer.clone_empty, :html_safe?
+    assert_not_predicate @buffer.gsub!("", "").clone_empty, :html_safe?
   end
 
   test "Should be safe when sliced if original value was safe" do
diff --git a/activesupport/test/string_inquirer_test.rb b/activesupport/test/string_inquirer_test.rb
index bf8f878a32..09726b144a 100644
--- a/activesupport/test/string_inquirer_test.rb
+++ b/activesupport/test/string_inquirer_test.rb
@@ -8,11 +8,11 @@ class StringInquirerTest < ActiveSupport::TestCase
   end
 
   def test_match
-    assert @string_inquirer.production?
+    assert_predicate @string_inquirer, :production?
   end
 
   def test_miss
-    assert_not @string_inquirer.development?
+    assert_not_predicate @string_inquirer, :development?
   end
 
   def test_missing_question_mark
diff --git a/activesupport/test/tagged_logging_test.rb b/activesupport/test/tagged_logging_test.rb
index 5fd6a6b316..e2b41cf8ee 100644
--- a/activesupport/test/tagged_logging_test.rb
+++ b/activesupport/test/tagged_logging_test.rb
@@ -21,7 +21,7 @@ class TaggedLoggingTest < ActiveSupport::TestCase
     assert_nil logger.formatter
     ActiveSupport::TaggedLogging.new(logger)
     assert_not_nil logger.formatter
-    assert logger.formatter.respond_to?(:tagged)
+    assert_respond_to logger.formatter, :tagged
   end
 
   test "tagged once" do
@@ -74,11 +74,12 @@ class TaggedLoggingTest < ActiveSupport::TestCase
   test "keeps each tag in their own thread" do
     @logger.tagged("BCX") do
       Thread.new do
+        @logger.info "Dull story"
         @logger.tagged("OMG") { @logger.info "Cool story" }
       end.join
       @logger.info "Funky time"
     end
-    assert_equal "[OMG] Cool story\n[BCX] Funky time\n", @output.string
+    assert_equal "Dull story\n[OMG] Cool story\n[BCX] Funky time\n", @output.string
   end
 
   test "keeps each tag in their own instance" do
diff --git a/activesupport/test/test_case_test.rb b/activesupport/test/test_case_test.rb
index 79b75a001a..eced622137 100644
--- a/activesupport/test/test_case_test.rb
+++ b/activesupport/test/test_case_test.rb
@@ -115,6 +115,35 @@ class AssertDifferenceTest < ActiveSupport::TestCase
     end
   end
 
+  def test_hash_of_expressions
+    assert_difference "@object.num" => 1, "@object.num + 1" => 1 do
+      @object.increment
+    end
+  end
+
+  def test_hash_of_expressions_with_message
+    error = assert_raises Minitest::Assertion do
+      assert_difference({ "@object.num" => 0 }, "Object Changed") do
+        @object.increment
+      end
+    end
+    assert_equal "Object Changed.\n\"@object.num\" didn't change by 0.\nExpected: 0\n  Actual: 1", error.message
+  end
+
+  def test_hash_of_lambda_expressions
+    assert_difference -> { @object.num } => 1, -> { @object.num + 1 } => 1 do
+      @object.increment
+    end
+  end
+
+  def test_hash_of_expressions_identify_failure
+    assert_raises(Minitest::Assertion) do
+      assert_difference "@object.num" => 1, "1 + 1" => 1 do
+        @object.increment
+      end
+    end
+  end
+
   def test_assert_changes_pass
     assert_changes "@object.num" do
       @object.increment
diff --git a/activesupport/test/time_zone_test.rb b/activesupport/test/time_zone_test.rb
index 405c8f315b..63ca22efb5 100644
--- a/activesupport/test/time_zone_test.rb
+++ b/activesupport/test/time_zone_test.rb
@@ -756,6 +756,16 @@ class TimeZoneTest < ActiveSupport::TestCase
     assert_not_includes ActiveSupport::TimeZone.country_zones(:ru), ActiveSupport::TimeZone["Kuala Lumpur"]
   end
 
+  def test_country_zones_with_and_without_mappings
+    assert_includes ActiveSupport::TimeZone.country_zones("au"), ActiveSupport::TimeZone["Adelaide"]
+    assert_includes ActiveSupport::TimeZone.country_zones("au"), ActiveSupport::TimeZone["Australia/Lord_Howe"]
+  end
+
+  def test_country_zones_with_multiple_mappings
+    assert_includes ActiveSupport::TimeZone.country_zones("gb"), ActiveSupport::TimeZone["Edinburgh"]
+    assert_includes ActiveSupport::TimeZone.country_zones("gb"), ActiveSupport::TimeZone["London"]
+  end
+
   def test_country_zones_without_mappings
     assert_includes ActiveSupport::TimeZone.country_zones(:sv), ActiveSupport::TimeZone["America/El_Salvador"]
   end
diff --git a/ci/qunit-selenium-runner.rb b/ci/qunit-selenium-runner.rb
index 3a58377d77..05bcab8cdb 100644
--- a/ci/qunit-selenium-runner.rb
+++ b/ci/qunit-selenium-runner.rb
@@ -6,6 +6,7 @@ require "chromedriver/helper"
 driver_options = Selenium::WebDriver::Chrome::Options.new
 driver_options.add_argument("--headless")
 driver_options.add_argument("--disable-gpu")
+driver_options.add_argument("--no-sandbox")
 
 driver = ::Selenium::WebDriver.for(:chrome, options: driver_options)
 result = QUnit::Selenium::TestRunner.new(driver).open(ARGV[0], timeout: 60)
diff --git a/ci/travis.rb b/ci/travis.rb
index f521ef3cf6..861063afa5 100755
--- a/ci/travis.rb
+++ b/ci/travis.rb
@@ -159,7 +159,7 @@ results = {}
 ENV["GEM"].split(",").each do |gem|
   [false, true].each do |isolated|
     next if ENV["TRAVIS_PULL_REQUEST"] && ENV["TRAVIS_PULL_REQUEST"] != "false" && isolated
-    next if RUBY_VERSION < "2.4" && isolated
+    next if RUBY_VERSION < "2.5" && isolated
     next if gem == "railties" && isolated
     next if gem == "ac" && isolated
     next if gem == "ac:integration" && isolated
diff --git a/guides/CHANGELOG.md b/guides/CHANGELOG.md
index 518b6abfb3..21b4ed4b9f 100644
--- a/guides/CHANGELOG.md
+++ b/guides/CHANGELOG.md
@@ -1,10 +1,8 @@
-## Rails 5.2.0.beta2 (November 28, 2017) ##
+## Rails 6.0.0.alpha (Unreleased) ##
 
-*   No changes.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
+    *Jeremy Daer*
 
-## Rails 5.2.0.beta1 (November 27, 2017) ##
 
-*   No changes.
-
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/guides/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/guides/CHANGELOG.md) for previous changes.
diff --git a/guides/bug_report_templates/action_controller_gem.rb b/guides/bug_report_templates/action_controller_gem.rb
index 557b1d7bef..7fc85e636a 100644
--- a/guides/bug_report_templates/action_controller_gem.rb
+++ b/guides/bug_report_templates/action_controller_gem.rb
@@ -13,7 +13,7 @@ gemfile(true) do
   git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
   # Activate the gem you are reporting the issue against.
-  gem "rails", "5.1.0"
+  gem "rails", "5.2.0.rc1"
 end
 
 require "rack/test"
diff --git a/guides/bug_report_templates/active_job_gem.rb b/guides/bug_report_templates/active_job_gem.rb
index 013d1f8602..6b30a7d446 100644
--- a/guides/bug_report_templates/active_job_gem.rb
+++ b/guides/bug_report_templates/active_job_gem.rb
@@ -13,7 +13,7 @@ gemfile(true) do
   git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
   # Activate the gem you are reporting the issue against.
-  gem "activejob", "5.1.0"
+  gem "activejob", "5.2.0.rc1"
 end
 
 require "minitest/autorun"
diff --git a/guides/bug_report_templates/active_record_gem.rb b/guides/bug_report_templates/active_record_gem.rb
index 921917fbe9..fabc2a2382 100644
--- a/guides/bug_report_templates/active_record_gem.rb
+++ b/guides/bug_report_templates/active_record_gem.rb
@@ -13,7 +13,7 @@ gemfile(true) do
   git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
   # Activate the gem you are reporting the issue against.
-  gem "activerecord", "5.1.0"
+  gem "activerecord", "5.2.0.rc1"
   gem "sqlite3"
 end
 
diff --git a/guides/bug_report_templates/active_record_migrations_gem.rb b/guides/bug_report_templates/active_record_migrations_gem.rb
index 9002b8f428..ca9987f956 100644
--- a/guides/bug_report_templates/active_record_migrations_gem.rb
+++ b/guides/bug_report_templates/active_record_migrations_gem.rb
@@ -13,7 +13,7 @@ gemfile(true) do
   git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
   # Activate the gem you are reporting the issue against.
-  gem "activerecord", "5.1.0"
+  gem "activerecord", "5.2.0.rc1"
   gem "sqlite3"
 end
 
@@ -37,7 +37,7 @@ end
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[5.1]
+class ChangeAmountToAddScale < ActiveRecord::Migration[5.2]
   def change
     reversible do |dir|
       dir.up do
diff --git a/guides/bug_report_templates/active_record_migrations_master.rb b/guides/bug_report_templates/active_record_migrations_master.rb
index 194b093ac3..715dca98ba 100644
--- a/guides/bug_report_templates/active_record_migrations_master.rb
+++ b/guides/bug_report_templates/active_record_migrations_master.rb
@@ -36,7 +36,7 @@ end
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[5.2]
+class ChangeAmountToAddScale < ActiveRecord::Migration[6.0]
   def change
     reversible do |dir|
       dir.up do
diff --git a/guides/bug_report_templates/generic_gem.rb b/guides/bug_report_templates/generic_gem.rb
index 60e8322c2a..7a55d7c660 100644
--- a/guides/bug_report_templates/generic_gem.rb
+++ b/guides/bug_report_templates/generic_gem.rb
@@ -13,9 +13,10 @@ gemfile(true) do
   git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
   # Activate the gem you are reporting the issue against.
-  gem "activesupport", "5.1.0"
+  gem "activesupport", "5.2.0.rc1"
 end
 
+require "active_support"
 require "active_support/core_ext/object/blank"
 require "minitest/autorun"
 
diff --git a/guides/rails_guides/kindle.rb b/guides/rails_guides/kindle.rb
index 87a369a15a..5c4f7d159c 100644
--- a/guides/rails_guides/kindle.rb
+++ b/guides/rails_guides/kindle.rb
@@ -58,9 +58,9 @@ module Kindle
   end
 
   def generate_sections(html_pages)
-    FileUtils::rm_rf("sections/")
+    FileUtils.rm_rf("sections/")
     html_pages.each_with_index do |page, section_idx|
-      FileUtils::mkdir_p("sections/%03d" % section_idx)
+      FileUtils.mkdir_p("sections/%03d" % section_idx)
       doc = Nokogiri::HTML(File.open(page))
       title = doc.at("title").inner_text.gsub("Ruby on Rails Guides: ", "")
       title = page.capitalize.gsub(".html", "") if title.strip == ""
diff --git a/guides/source/active_job_basics.md b/guides/source/active_job_basics.md
index 914ef2c327..97d98efba0 100644
--- a/guides/source/active_job_basics.md
+++ b/guides/source/active_job_basics.md
@@ -276,7 +276,7 @@ class GuestsCleanupJob < ApplicationJob
   end
 
   private
-    def around_cleanup(job)
+    def around_cleanup
       # Do something before perform
       yield
       # Do something after perform
@@ -339,8 +339,23 @@ UserMailer.welcome(@user).deliver_later # Email will be localized to Esperanto.
 ```
 
 
-GlobalID
---------
+Supported types for arguments
+----------------------------
+
+ActiveJob supports the following types of arguments by default:
+
+  - Basic types (`NilClass`, `String`, `Integer`, `Float`, `BigDecimal`, `TrueClass`, `FalseClass`)
+  - `Symbol`
+  - `Date`
+  - `Time`
+  - `DateTime`
+  - `ActiveSupport::TimeWithZone`
+  - `ActiveSupport::Duration`
+  - `Hash` (Keys should be of `String` or `Symbol` type)
+  - `ActiveSupport::HashWithIndifferentAccess`
+  - `Array`
+
+### GlobalID
 
 Active Job supports GlobalID for parameters. This makes it possible to pass live
 Active Record objects to your job instead of class/id pairs, which you then have
@@ -368,6 +383,39 @@ end
 This works with any class that mixes in `GlobalID::Identification`, which
 by default has been mixed into Active Record classes.
 
+### Serializers
+
+You can extend the list of supported argument types. You just need to define your own serializer:
+
+```ruby
+class MoneySerializer < ActiveJob::Serializers::ObjectSerializer
+  # Checks if an argument should be serialized by this serializer.
+  def serialize?(argument)
+    argument.is_a? Money
+  end
+
+  # Converts an object to a simpler representative using supported object types.
+  # The recommended representative is a Hash with a specific key. Keys can be of basic types only.
+  # You should call `super` to add the custom serializer type to the hash.
+  def serialize(money)
+    super(
+      "amount" => money.amount,
+      "currency" => money.currency
+    )
+  end
+
+  # Converts serialized value into a proper object.
+  def deserialize(hash)
+    Money.new(hash["amount"], hash["currency"])
+  end
+end
+```
+
+and add this serializer to the list:
+
+```ruby
+Rails.application.config.active_job.custom_serializers << MoneySerializer
+```
 
 Exceptions
 ----------
diff --git a/guides/source/active_record_basics.md b/guides/source/active_record_basics.md
index 9be9c6c7b7..2f85b765a3 100644
--- a/guides/source/active_record_basics.md
+++ b/guides/source/active_record_basics.md
@@ -45,6 +45,8 @@ relationships of the objects in an application can be easily stored and
 retrieved from a database without writing SQL statements directly and with less
 overall database access code.
 
+NOTE: If you are not familiar enough with relational database management systems (RDBMS) or structured query language (SQL), please go through [this tutorial](https://www.w3schools.com/sql/default.asp) (or [this one](http://www.sqlcourse.com/)) or study them by other means. Understanding how relational databases work is crucial to understanding Active Records and Rails in general.
+
 ### Active Record as an ORM Framework
 
 Active Record gives us several mechanisms, the most important being the ability
@@ -142,7 +144,7 @@ end
 This will create a `Product` model, mapped to a `products` table at the
 database. By doing this you'll also have the ability to map the columns of each
 row in that table with the attributes of the instances of your model. Suppose
-that the `products` table was created using an SQL statement like:
+that the `products` table was created using an SQL (or one of its extensions) statement like:
 
 ```sql
 CREATE TABLE products (
@@ -152,8 +154,9 @@ CREATE TABLE products (
 );
 ```
 
-Following the table schema above, you would be able to write code like the
-following:
+Schema above declares a table with two columns: `id` and `name`. Each row of
+this table represents a certain product with these two parameters. Thus, you
+would be able to write code like the following:
 
 ```ruby
 p = Product.new
diff --git a/guides/source/active_record_callbacks.md b/guides/source/active_record_callbacks.md
index 630dafe632..4f54b4c206 100644
--- a/guides/source/active_record_callbacks.md
+++ b/guides/source/active_record_callbacks.md
@@ -264,7 +264,7 @@ The whole callback chain is wrapped in a transaction. If any callback raises an
 throw :abort
 ```
 
-WARNING. Any exception that is not `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` will be re-raised by Rails after the callback chain is halted. Raising an exception other than `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` may break code that does not expect methods like `save` and `update_attributes` (which normally try to return `true` or `false`) to raise an exception.
+WARNING. Any exception that is not `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` will be re-raised by Rails after the callback chain is halted. Raising an exception other than `ActiveRecord::Rollback` or `ActiveRecord::RecordInvalid` may break code that does not expect methods like `save` and `update` (which normally try to return `true` or `false`) to raise an exception.
 
 Relational Callbacks
 --------------------
diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md
index c5bd09ead6..a7cb14c52a 100644
--- a/guides/source/active_storage_overview.md
+++ b/guides/source/active_storage_overview.md
@@ -49,12 +49,10 @@ below declares three services named `local`, `test`, and `amazon`:
 local:
   service: Disk
   root: <%= Rails.root.join("storage") %>
-  host: http://localhost:3000
 
 test:
   service: Disk
   root: <%= Rails.root.join("tmp/storage") %>
-  host: http://localhost:3000
 
 amazon:
   service: S3
@@ -93,7 +91,15 @@ Declare a Disk service in `config/storage.yml`:
 local:
   service: Disk
   root: <%= Rails.root.join("storage") %>
-  host: http://localhost:3000
+```
+
+Optionally specify a host for generating URLs (the default is `http://localhost:3000`):
+
+```yaml
+local:
+  service: Disk
+  root: <%= Rails.root.join("storage") %>
+  host: http://myapp.test
 ```
 
 ### Amazon S3 Service
@@ -115,6 +121,8 @@ Add the [`aws-sdk-s3`](https://github.com/aws/aws-sdk-ruby) gem to your `Gemfile
 gem "aws-sdk-s3", require: false
 ```
 
+NOTE: The core features of Active Storage require the following permissions: `s3:ListBucket`, `s3:PutObject`, `s3:GetObject`, and `s3:DeleteObject`. If you have additional upload options configured such as setting ACLs then additional permissions may be required.
+
 ### Microsoft Azure Storage Service
 
 Declare an Azure Storage service in `config/storage.yml`:
@@ -169,7 +177,7 @@ google:
 Add the [`google-cloud-storage`](https://github.com/GoogleCloudPlatform/google-cloud-ruby/tree/master/google-cloud-storage) gem to your `Gemfile`:
 
 ```ruby
-gem "google-cloud-storage", "~> 1.3", require: false
+gem "google-cloud-storage", "~> 1.8", require: false
 ```
 
 ### Mirror Service
@@ -550,6 +558,30 @@ config.active_job.queue_adapter = :inline
 config.active_storage.service = :local_test
 ```
 
+Discarding Files Stored During Integration Tests
+-------------------------------------------
+
+Similarly to System Tests, files uploaded during Integration Tests will not be
+automatically cleaned up. If you want to clear the files, you can do it in an
+`after_teardown` callback. Doing it here ensures that all connections created
+during the test are complete and you won't receive an error from Active Storage
+saying it can't find a file.
+
+```ruby
+module ActionDispatch
+  class IntegrationTest
+    def remove_uploaded_files
+      FileUtils.rm_rf(Rails.root.join('tmp', 'storage'))
+    end
+
+    def after_teardown
+      super
+      remove_uploaded_files
+    end
+  end
+end
+```
+
 Implementing Support for Other Cloud Services
 ---------------------------------------------
 
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 8e2826bb85..73b24b900a 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -135,16 +135,14 @@ NOTE: Defined in `active_support/core_ext/object/blank.rb`.
 
 ### `duplicable?`
 
-In Ruby 2.4 most objects can be duplicated via `dup` or `clone` except
-methods and certain numbers. Though Ruby 2.2 and 2.3 can't duplicate `nil`,
-`false`, `true`, and  symbols as well as instances `Float`, `Fixnum`,
-and `Bignum` instances.
+As of Ruby 2.5, most objects can be duplicated via `dup` or `clone`:
 
 ```ruby
 "foo".dup           # => "foo"
 "".dup              # => ""
-1.method(:+).dup    # => TypeError: allocator undefined for Method
-Complex(0).dup      # => TypeError: can't copy Complex
+Rational(1).dup     # => (1/1)
+Complex(0).dup      # => (0+0i)
+1.method(:+).dup    # => TypeError (allocator undefined for Method)
 ```
 
 Active Support provides `duplicable?` to query an object about this:
@@ -152,35 +150,18 @@ Active Support provides `duplicable?` to query an object about this:
 ```ruby
 "foo".duplicable?           # => true
 "".duplicable?              # => true
-Rational(1).duplicable?     # => false
-Complex(1).duplicable?      # => false
+Rational(1).duplicable?     # => true
+Complex(1).duplicable?      # => true
 1.method(:+).duplicable?    # => false
 ```
 
-`duplicable?` matches Ruby's `dup` according to the Ruby version.
-
-So in 2.4:
+`duplicable?` matches the current Ruby version's `dup` behavior,
+so results will vary according the version of Ruby you're using.
+In Ruby 2.4, for example, Complex and Rational are not duplicable:
 
 ```ruby
-nil.dup                 # => nil
-:my_symbol.dup          # => :my_symbol
-1.dup                   # => 1
-
-nil.duplicable?         # => true
-:my_symbol.duplicable?  # => true
-1.duplicable?           # => true
-```
-
-Whereas in 2.2 and 2.3:
-
-```ruby
-nil.dup                 # => TypeError: can't dup NilClass
-:my_symbol.dup          # => TypeError: can't dup Symbol
-1.dup                   # => TypeError: can't dup Fixnum
-
-nil.duplicable?         # => false
-:my_symbol.duplicable?  # => false
-1.duplicable?           # => false
+Rational(1).duplicable?     # => false
+Complex(1).duplicable?      # => false
 ```
 
 WARNING: Any class can disallow duplication by removing `dup` and `clone` or raising exceptions from them. Thus only `rescue` can tell whether a given arbitrary object is duplicable. `duplicable?` depends on the hard-coded list above, but it is much faster than `rescue`. Use it only if you know the hard-coded list is enough in your use case.
@@ -925,6 +906,15 @@ The macros `cattr_reader`, `cattr_writer`, and `cattr_accessor` are analogous to
 ```ruby
 class MysqlAdapter < AbstractAdapter
   # Generates class methods to access @@emulate_booleans.
+  cattr_accessor :emulate_booleans
+end
+```
+
+Also, you can pass a block to `cattr_*` to set up the attribute with a default value:
+
+```ruby
+class MysqlAdapter < AbstractAdapter
+  # Generates class methods to access @@emulate_booleans with default value of true.
   cattr_accessor :emulate_booleans, default: true
 end
 ```
@@ -941,15 +931,6 @@ end
 
 we can access `field_error_proc` in views.
 
-Also, you can pass a block to `cattr_*` to set up the attribute with a default value:
-
-```ruby
-class MysqlAdapter < AbstractAdapter
-  # Generates class methods to access @@emulate_booleans with default value of true.
-  cattr_accessor :emulate_booleans, default: true
-end
-```
-
 The generation of the reader instance method can be prevented by setting `:instance_reader` to `false` and the generation of the writer instance method can be prevented by setting `:instance_writer` to `false`. Generation of both methods can be prevented by setting `:instance_accessor` to `false`. In all cases, the value must be exactly `false` and not any false value.
 
 ```ruby
@@ -2776,20 +2757,6 @@ Active Record does not accept unknown options when building associations, for ex
 
 NOTE: Defined in `active_support/core_ext/hash/keys.rb`.
 
-### Working with Values
-
-#### `transform_values` && `transform_values!`
-
-The method `transform_values` accepts a block and returns a hash that has applied the block operations to each of the values in the receiver.
-
-```ruby
-{ nil => nil, 1 => 1, :x => :a }.transform_values { |value| value.to_s.upcase }
-# => {nil=>"", 1=>"1", :x=>"A"}
-```
-There's also the bang variant `transform_values!` that applies the block operations to values in the very receiver.
-
-NOTE: Defined in `active_support/core_ext/hash/transform_values.rb`.
-
 ### Slicing
 
 Ruby has built-in support for taking slices out of strings and arrays. Active Support extends slicing to hashes:
@@ -2890,24 +2857,6 @@ end
 
 NOTE: Defined in `active_support/core_ext/regexp.rb`.
 
-### `match?`
-
-Rails implements `Regexp#match?` for Ruby versions prior to 2.4:
-
-```ruby
-/oo/.match?('foo')    # => true
-/oo/.match?('bar')    # => false
-/oo/.match?('foo', 1) # => true
-```
-
-The backport has the same interface and lack of side-effects in the caller like
-not setting `$1` and friends, but it does not have the speed benefits. Its
-purpose is to be able to write 2.4 compatible code. Rails itself uses this
-predicate internally for example.
-
-Active Support defines `Regexp#match?` only if not present, so code running
-under 2.4 or later does run the original one and gets the performance boost.
-
 Extensions to `Range`
 ---------------------
 
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index e6d5aed135..618896d458 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -22,8 +22,7 @@ The asset pipeline provides a framework to concatenate and minify or compress
 JavaScript and CSS assets. It also adds the ability to write these assets in
 other languages and pre-processors such as CoffeeScript, Sass and ERB.
 It allows assets in your application to be automatically combined with assets
-from other gems. For example, jquery-rails includes a copy of jquery.js
-and enables AJAX features in Rails.
+from other gems.
 
 The asset pipeline is implemented by the
 [sprockets-rails](https://github.com/rails/sprockets-rails) gem,
@@ -1205,10 +1204,10 @@ Adding Assets to Your Gems
 
 Assets can also come from external sources in the form of gems.
 
-A good example of this is the `jquery-rails` gem which comes with Rails as the
-standard JavaScript library gem. This gem contains an engine class which
-inherits from `Rails::Engine`. By doing this, Rails is informed that the
-directory for this gem may contain assets and the `app/assets`, `lib/assets` and
+A good example of this is the `jquery-rails` gem.
+This gem contains an engine class which inherits from `Rails::Engine`.
+By doing this, Rails is informed that the directory for this
+gem may contain assets and the `app/assets`, `lib/assets` and
 `vendor/assets` directories of this engine are added to the search path of
 Sprockets.
 
@@ -1244,11 +1243,7 @@ moving the files from `public/` to the new locations. See [Asset
 Organization](#asset-organization) above for guidance on the correct locations
 for different file types.
 
-Next will be avoiding duplicate JavaScript files. Since jQuery is the default
-JavaScript library from Rails 3.1 onwards, you don't need to copy `jquery.js`
-into `app/assets` and it will be included automatically.
-
-The third is updating the various environment files with the correct default
+Next is updating the various environment files with the correct default
 options.
 
 In `application.rb`:
diff --git a/guides/source/association_basics.md b/guides/source/association_basics.md
index 02d012d702..f895cadea5 100644
--- a/guides/source/association_basics.md
+++ b/guides/source/association_basics.md
@@ -572,40 +572,32 @@ class Book < ApplicationRecord
 end
 ```
 
-This declaration needs to be backed up by the proper foreign key declaration on the books table:
+This declaration needs to be backed up by a corresponding foreign key column in the books table. For a brand new table, the migration might look something like this:
 
 ```ruby
 class CreateBooks < ActiveRecord::Migration[5.0]
   def change
     create_table :books do |t|
-      t.datetime :published_at
-      t.string   :book_number
-      t.integer  :author_id
+      t.datetime   :published_at
+      t.string     :book_number
+      t.references :author
     end
   end
 end
 ```
 
-If you create an association some time after you build the underlying model, you need to remember to create an `add_column` migration to provide the necessary foreign key.
-
-It's a good practice to add an index on the foreign key to improve queries
-performance and a foreign key constraint to ensure referential data integrity:
+Whereas for an existing table, it might look like this:
 
 ```ruby
-class CreateBooks < ActiveRecord::Migration[5.0]
+class AddAuthorToBooks < ActiveRecord::Migration[5.0]
   def change
-    create_table :books do |t|
-      t.datetime :published_at
-      t.string   :book_number
-      t.integer  :author_id
-    end
-
-    add_index :books, :author_id
-    add_foreign_key :books, :authors
+    add_reference :books, :author
   end
 end
 ```
 
+NOTE: If you wish to [enforce referential integrity at the database level](/active_record_migrations.html#foreign-keys), add the `foreign_key: true` option to the ‘reference’ column declarations above.
+
 #### Creating Join Tables for `has_and_belongs_to_many` Associations
 
 If you create a `has_and_belongs_to_many` association, you need to explicitly create the joining table. Unless the name of the join table is explicitly specified by using the `:join_table` option, Active Record creates the name by using the lexical book of the class names. So a join between author and book models will give the default join table name of "authors_books" because "a" outranks "b" in lexical ordering.
@@ -795,7 +787,7 @@ The `belongs_to` association creates a one-to-one match with another model. In d
 
 #### Methods Added by `belongs_to`
 
-When you declare a `belongs_to` association, the declaring class automatically gains five methods related to the association:
+When you declare a `belongs_to` association, the declaring class automatically gains 6 methods related to the association:
 
 * `association`
 * `association=(associate)`
@@ -1146,7 +1138,7 @@ The `has_one` association creates a one-to-one match with another model. In data
 
 #### Methods Added by `has_one`
 
-When you declare a `has_one` association, the declaring class automatically gains five methods related to the association:
+When you declare a `has_one` association, the declaring class automatically gains 6 methods related to the association:
 
 * `association`
 * `association=(associate)`
@@ -1419,7 +1411,7 @@ The `has_many` association creates a one-to-many relationship with another model
 
 #### Methods Added by `has_many`
 
-When you declare a `has_many` association, the declaring class automatically gains 16 methods related to the association:
+When you declare a `has_many` association, the declaring class automatically gains 17 methods related to the association:
 
 * `collection`
 * `collection<<(object, ...)`
@@ -1952,7 +1944,7 @@ The `has_and_belongs_to_many` association creates a many-to-many relationship wi
 
 #### Methods Added by `has_and_belongs_to_many`
 
-When you declare a `has_and_belongs_to_many` association, the declaring class automatically gains 16 methods related to the association:
+When you declare a `has_and_belongs_to_many` association, the declaring class automatically gains 17 methods related to the association:
 
 * `collection`
 * `collection<<(object, ...)`
diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md
index dea87a18f8..5428b16edc 100644
--- a/guides/source/autoloading_and_reloading_constants.md
+++ b/guides/source/autoloading_and_reloading_constants.md
@@ -8,7 +8,7 @@ This guide documents how constant autoloading and reloading works.
 After reading this guide, you will know:
 
 * Key aspects of Ruby constants
-* What is `autoload_paths`
+* What are the `autoload_paths` and how does eager loading work in production?
 * How constant autoloading works
 * What is `require_dependency`
 * How constant reloading works
@@ -430,8 +430,8 @@ if `House` is still unknown when `app/models/beach_house.rb` is being eager
 loaded, Rails autoloads it.
 
 
-autoload_paths
---------------
+autoload_paths and eager_load_paths
+-----------------------------------
 
 As you probably know, when `require` gets a relative file name:
 
@@ -451,7 +451,7 @@ the idea is that when a constant like `Post` is hit and missing, if there's a
 `post.rb` file for example in `app/models` Rails is going to find it, evaluate
 it, and have `Post` defined as a side-effect.
 
-Alright, Rails has a collection of directories similar to `$LOAD_PATH` in which
+All right, Rails has a collection of directories similar to `$LOAD_PATH` in which
 to look up `post.rb`. That collection is called `autoload_paths` and by
 default it contains:
 
@@ -465,17 +465,22 @@ default it contains:
 
 * The directory `test/mailers/previews`.
 
-Also, this collection is configurable via `config.autoload_paths`. For example,
-`lib` was in the list years ago, but no longer is. An application can opt-in
-by adding this to `config/application.rb`:
+`eager_load_paths` is initially the `app` paths above
 
-```ruby
-config.autoload_paths << "#{Rails.root}/lib"
-```
+How files are autoloaded depends on `eager_load` and `cache_classes` config settings which typically vary in development, production, and test modes:
+ 
+ * In **development**, you want quicker startup with incremental loading of application code.  So `eager_load` should be set to `false`, and Rails will autoload files as needed (see [Autoloading Algorithms](#autoloading-algorithms) below) -- and then reload them when they change (see [Constant Reloading](#constant-reloading) below).
+ * In **production**, however you want consistency and thread-safety and can live with a longer boot time. So `eager_load` is set to `true`, and then during boot (before the app is ready to receive requests) Rails loads all files in the `eager_load_paths`  and then turns off auto loading (NB: autoloading may be needed during eager loading). Not autoloading after boot is a `good thing`, as autoloading can cause the app to be have thread-safety problems. 
+ * In **test**, for speed of execution (of individual tests) `eager_load` is `false`, so Rails follows development behaviour. 
+
+What is described above are the defaults with a newly generated Rails app. There are multiple ways this can be configured differently (see [Configuring Rails Applications](configuring.html#rails-general-configuration).
+). But using `autoload_paths` on its own  in the past (before Rails 5) developers might configure `autoload_paths` to add in extra locations (e.g. `lib` which used to be an autoload path list years ago, but no longer is).  However this is now discouraged for most purposes, as it is likely to lead to production-only errors. It is possible to add new locations to both `config.eager_load_paths` and `config.autoload_paths` but use at your own risk.
+
+See also [Autoloading in the Test Environment](#autoloading-in-the-test-environment).
 
 `config.autoload_paths` is not changeable from environment-specific configuration files.
 
-The value of `autoload_paths` can be inspected. In a just generated application
+The value of `autoload_paths` can be inspected. In a just-generated application
 it is (edited):
 
 ```
@@ -1329,3 +1334,17 @@ class C < BasicObject
   end
 end
 ```
+
+### Autoloading in the Test Environment
+ 
+When configuring the `test` environment for autoloading you might consider multiple factors. 
+
+For example it might be worth running your tests with an identical setup to production (`config.eager_load = true`, `config.cache_classes = true`) in order to catch any problems before they hit production (this is compensation for the lack of dev-prod parity). However this will slow down the boot time for individual tests on a dev machine (and is not immediately compatible with spring see below). So one possibility is to do this on a 
+[CI](https://en.wikipedia.org/wiki/Continuous_integration) machine only (which should run without spring). 
+
+On a development machine you can then have your tests running with whatever is fastest (ideally `config.eager_load = false`). 
+
+With the [Spring](https://github.com/rails/spring) pre-loader (included with new Rails apps), you ideally keep `config.eager_load = false` as per development. Sometimes you may end up with a hybrid configuration (`config.eager_load = true`, `config.cache_classes = true` AND `config.enable_dependency_loading = true`), see [spring issue](https://github.com/rails/spring/issues/519#issuecomment-348324369). However it might be simpler to keep the same configuration as development, and work out whatever it is that is causing autoloading to fail (perhaps by the results of your CI test results). 
+
+Occasionally you may need to explicitly eager_load by using `Rails
+.application.eager_load!` in the setup of your tests -- this might occur if your [tests involve multithreading](https://stackoverflow.com/questions/25796409/in-rails-how-can-i-eager-load-all-code-before-a-specific-rspec-test). 
diff --git a/guides/source/caching_with_rails.md b/guides/source/caching_with_rails.md
index cd9f4b4a68..5dde6f34fa 100644
--- a/guides/source/caching_with_rails.md
+++ b/guides/source/caching_with_rails.md
@@ -465,6 +465,10 @@ is often faster than waiting more than a second to retrieve it. Both read and
 write timeouts default to 1 second, but may be set lower if your network is
 consistently low latency.
 
+By default, the cache store will not attempt to reconnect to Redis if the
+connection fails during a request. If you experience frequent disconnects you
+may wish to enable reconnect attempts.
+
 Cache reads and writes never raise exceptions. They just return `nil` instead,
 behaving as if there was nothing in the cache. To gauge whether your cache is
 hitting exceptions, you may provide an `error_handler` to report to an
@@ -480,9 +484,10 @@ like this:
 cache_servers = %w[ "redis://cache-01:6379/0", "redis://cache-02:6379/0", … ],
 config.cache_store = :redis_cache_store, url: cache_servers,
 
-  connect_timeout: 30,  # Defaults to 20 seconds
-  read_timeout:    0.2, # Defaults to 1 second
-  write_timeout:   0.2, # Defaults to 1 second
+  connect_timeout:    30,  # Defaults to 20 seconds
+  read_timeout:       0.2, # Defaults to 1 second
+  write_timeout:      0.2, # Defaults to 1 second
+  reconnect_attempts: 1,   # Defaults to 0
 
   error_handler: -> (method:, returning:, exception:) {
     # Report errors to Sentry as warnings
diff --git a/guides/source/command_line.md b/guides/source/command_line.md
index 648645af7c..b41e8bbec6 100644
--- a/guides/source/command_line.md
+++ b/guides/source/command_line.md
@@ -431,16 +431,16 @@ INFO: You can also use `bin/rails -T`  to get the list of tasks.
 ```bash
 $ bin/rails about
 About your application's environment
-Rails version             5.1.0
-Ruby version              2.2.2 (x86_64-linux)
-RubyGems version          2.4.6
-Rack version              2.0.1
+Rails version             6.0.0
+Ruby version              2.5.0 (x86_64-linux)
+RubyGems version          2.7.3
+Rack version              2.0.4
 JavaScript Runtime        Node.js (V8)
 Middleware:               Rack::Sendfile, ActionDispatch::Static, ActionDispatch::Executor, ActiveSupport::Cache::Strategy::LocalCache::Middleware, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, ActionDispatch::RemoteIp, Sprockets::Rails::QuietAssets, Rails::Rack::Logger, ActionDispatch::ShowExceptions, WebConsole::Middleware, ActionDispatch::DebugExceptions, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, Rack::Head, Rack::ConditionalGet, Rack::ETag
 Application root          /home/foobar/commandsapp
 Environment               development
 Database adapter          sqlite3
-Database schema version   20110805173523
+Database schema version   20180205173523
 ```
 
 ### `assets`
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 879a1ea89f..fd747c1686 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -62,7 +62,7 @@ These configuration methods are to be called on a `Rails::Railtie` object, such
 
 * `config.autoload_once_paths` accepts an array of paths from which Rails will autoload constants that won't be wiped per request. Relevant if `config.cache_classes` is `false`, which is the case in development mode by default. Otherwise, all autoloading happens only once. All elements of this array must also be in `autoload_paths`. Default is an empty array.
 
-* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`.
+* `config.autoload_paths` accepts an array of paths from which Rails will autoload constants. Default is all directories under `app`. It is no longer recommended to adjust this. See [Autoloading and Reloading Constants](autoloading_and_reloading_constants.html#autoload-paths-and-eager-load-paths)
 
 * `config.cache_classes` controls whether or not application classes and modules should be reloaded on each request. Defaults to `false` in development mode, and `true` in test and production modes.
 
@@ -200,6 +200,7 @@ The full set of methods that can be used in this block are as follows:
 * `force_plural` allows pluralized model names. Defaults to `false`.
 * `helper` defines whether or not to generate helpers. Defaults to `true`.
 * `integration_tool` defines which integration tool to use to generate integration tests. Defaults to `:test_unit`.
+* `system_tests` defines which integration tool to use to generate system tests. Defaults to `:test_unit`.
 * `javascripts` turns on the hook for JavaScript files in generators. Used in Rails for when the `scaffold` generator is run. Defaults to `true`.
 * `javascript_engine` configures the engine to be used (for eg. coffee) when generating assets. Defaults to `:js`.
 * `orm` defines which orm to use. Defaults to `false` and will use Active Record by default.
@@ -461,7 +462,10 @@ The schema dumper adds one additional configuration option:
     config.action_dispatch.default_headers = {
       'X-Frame-Options' => 'SAMEORIGIN',
       'X-XSS-Protection' => '1; mode=block',
-      'X-Content-Type-Options' => 'nosniff'
+      'X-Content-Type-Options' => 'nosniff',
+      'X-Download-Options' => 'noopen',
+      'X-Permitted-Cross-Domain-Policies' => 'none',
+      'Referrer-Policy' => 'strict-origin-when-cross-origin'
     }
     ```
 
@@ -737,6 +741,8 @@ There are a few configuration options available in Active Support:
 
 * `config.active_job.logger` accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Active Job. You can retrieve this logger by calling `logger` on either an Active Job class or an Active Job instance. Set to `nil` to disable logging.
 
+* `config.active_job.custom_serializers` allows to set custom argument serializers. Defaults to `[]`.
+
 ### Configuring Action Cable
 
 * `config.action_cable.url` accepts a string for the URL for where
@@ -748,6 +754,41 @@ main application.
 You can set this as nil to not mount Action Cable as part of your
 normal Rails server.
 
+
+### Configuring Active Storage
+
+`config.active_storage` provides the following configuration options:
+
+* `config.active_storage.analyzers` accepts an array of classes indicating the analyzers available for Active Storage blobs. The default is `[ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer]`. The former can extract width and height of an image blob; the latter can extract width, height, duration, angle, and aspect ratio of a video blob.
+
+* `config.active_storage.previewers` accepts an array of classes indicating the image previewers available in Active Storage blobs. The default is `[ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer]`. The former can generate a thumbnail from the first page of a PDF blob; the latter from the relevant frame of a video blob.
+
+* `config.active_storage.paths` accepts a hash of options indicating the locations of previewer/analyzer commands. The default is `{}`, meaning the commands will be looked for in the default path. Can include any of these options:
+    * `:ffprobe` - The location of the ffprobe executable.
+    * `:mutool` - The location of the mutool executable.
+    * `:ffmpeg` - The location of the ffmpeg executable.
+
+   ```ruby
+   config.active_storage.paths[:ffprobe] = '/usr/local/bin/ffprobe'
+   ```
+
+* `config.active_storage.variable_content_types` accepts an array of strings indicating the content types that Active Storage can transform through ImageMagick. The default is `%w(image/png image/gif image/jpg image/jpeg image/vnd.adobe.photoshop)`.
+
+* `config.active_storage.content_types_to_serve_as_binary` accepts an array of strings indicating the content types that Active Storage will always serve as an attachment, rather than inline. The default is `%w(text/html
+text/javascript image/svg+xml application/postscript application/x-shockwave-flash text/xml application/xml application/xhtml+xml)`.
+
+* `config.active_storage.queue` can be used to set the name of the Active Job queue used to perform jobs like analyzing the content of a blob or purging a blog.
+
+  ```ruby
+  config.active_job.queue = :low_priority
+  ```
+
+* `config.active_storage.logger` can be used to set the logger used by Active Storage. Accepts a logger conforming to the interface of Log4r or the default Ruby Logger class.
+
+  ```ruby
+  config.active_job.logger = ActiveSupport::Logger.new(STDOUT)
+  ```
+
 ### Configuring a Database
 
 Just about every Rails application will interact with a database. You can connect to the database by setting an environment variable `ENV['DATABASE_URL']` or by using a configuration file called `config/database.yml`.
diff --git a/guides/source/contributing_to_ruby_on_rails.md b/guides/source/contributing_to_ruby_on_rails.md
index 967c992c05..c1668f989b 100644
--- a/guides/source/contributing_to_ruby_on_rails.md
+++ b/guides/source/contributing_to_ruby_on_rails.md
@@ -134,7 +134,8 @@ learn about Ruby on Rails, and the API, which serves as a reference.
 
 You can help improve the Rails guides by making them more coherent, consistent or readable, adding missing information, correcting factual errors, fixing typos, or bringing them up to date with the latest edge Rails.
 
-To do so, open a pull request to [Rails](https://github.com/rails/rails) on GitHub.
+To do so, make changes to Rails guides source files (located [here](https://github.com/rails/rails/tree/master/guides/source) on GitHub). Then open a pull request to apply your
+changes to master branch.
 
 When working with documentation, please take into account the [API Documentation Guidelines](api_documentation_guidelines.html) and the [Ruby on Rails Guides Guidelines](ruby_on_rails_guides_guidelines.html).
 
diff --git a/guides/source/getting_started.md b/guides/source/getting_started.md
index b007baea87..f545b90103 100644
--- a/guides/source/getting_started.md
+++ b/guides/source/getting_started.md
@@ -87,10 +87,10 @@ current version of Ruby installed:
 
 ```bash
 $ ruby -v
-ruby 2.3.1p112
+ruby 2.5.0
 ```
 
-Rails requires Ruby version 2.2.2 or later. If the version number returned is
+Rails requires Ruby version 2.4.1 or later. If the version number returned is
 less than that number, you'll need to install a fresh copy of Ruby.
 
 TIP: A number of tools exist to help you quickly install Ruby and Ruby
@@ -100,7 +100,7 @@ For more installation methods for most Operating Systems take a look at
 [ruby-lang.org](https://www.ruby-lang.org/en/documentation/installation/).
 
 If you are working on Windows, you should also install the
-[Ruby Installer Development Kit](http://rubyinstaller.org/downloads/).
+[Ruby Installer Development Kit](https://rubyinstaller.org/downloads/).
 
 You will also need an installation of the SQLite3 database.
 Many popular UNIX-like OSes ship with an acceptable version of SQLite3.
@@ -170,7 +170,7 @@ of the files and folders that Rails created by default:
 | File/Folder | Purpose |
 | ----------- | ------- |
 |app/|Contains the controllers, models, views, helpers, mailers, channels, jobs and assets for your application. You'll focus on this folder for the remainder of this guide.|
-|bin/|Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy or run your application.|
+|bin/|Contains the rails script that starts your app and can contain other scripts you use to setup, update, deploy, or run your application.|
 |config/|Configure your application's routes, database, and more. This is covered in more detail in [Configuring Rails Applications](configuring.html).|
 |config.ru|Rack configuration for Rack based servers used to start the application. For more information about Rack, see the [Rack website](https://rack.github.io/).|
 |db/|Contains your current database schema, as well as the database migrations.|
@@ -346,9 +346,9 @@ Now that you've seen how to create a controller, an action and a view, let's
 create something with a bit more substance.
 
 In the Blog application, you will now create a new _resource_. A resource is the
-term used for a collection of similar objects, such as articles, people or
+term used for a collection of similar objects, such as articles, people, or
 animals.
-You can create, read, update and destroy items for a resource and these
+You can create, read, update, and destroy items for a resource and these
 operations are referred to as _CRUD_ operations.
 
 Rails provides a `resources` method which can be used to declare a standard REST
@@ -462,8 +462,7 @@ You're getting this error now because Rails expects plain actions like this one
 to have views associated with them to display their information. With no view
 available, Rails will raise an exception.
 
-In the above image, the bottom line has been truncated. Let's see what the full
-error message looks like:
+Let's look at the full error message again:
 
 >ArticlesController#new is missing a template for this request format and variant. request.formats: ["text/html"] request.variant: [] NOTE! For XHR/Ajax or API requests, this action would normally respond with 204 No Content: an empty white screen. Since you're loading it in a web browser, we assume that you expected to actually render a template, not… nothing, so we're showing an error to be extra-clear. If you expect 204 No Content, carry on. That's what you'll get from an XHR or API request. Give it a shot.
 
@@ -505,7 +504,7 @@ write this content in it:
 ```
 
 When you refresh <http://localhost:3000/articles/new> you'll now see that the
-page has a title. The route, controller, action and view are now working
+page has a title. The route, controller, action, and view are now working
 harmoniously! It's time to create the form for a new article.
 
 ### The first form
@@ -1123,7 +1122,7 @@ that otherwise `@article` would be `nil` in our view, and calling
 `@article.errors.any?` would throw an error.
 
 TIP: Rails automatically wraps fields that contain an error with a div
-with class `field_with_errors`. You can define a css rule to make them
+with class `field_with_errors`. You can define a CSS rule to make them
 standout.
 
 Now you'll get a nice error message when saving an article without title when
@@ -1205,10 +1204,10 @@ it look as follows:
 This time we point the form to the `update` action, which is not defined yet
 but will be very soon.
 
-Passing the article object to the method, will automagically create url for submitting the edited article form.
-This option tells Rails that we want this form to be submitted
-via the `PATCH` HTTP method which is the HTTP method you're expected to use to
-**update** resources according to the REST protocol.
+Passing the article object to the method will automatically set the URL for
+submitting the edited article form. This option tells Rails that we want this
+form to be submitted via the `PATCH` HTTP method, which is the HTTP method you're
+expected to use to **update** resources according to the REST protocol.
 
 The arguments to `form_with` could be model objects, say, `model: @article` which would
 cause the helper to fill in the form with the fields of the object. Passing in a
@@ -1507,7 +1506,7 @@ appear.
 TIP: Learn more about Unobtrusive JavaScript on
 [Working With JavaScript in Rails](working_with_javascript_in_rails.html) guide.
 
-Congratulations, you can now create, show, list, update and destroy
+Congratulations, you can now create, show, list, update, and destroy
 articles.
 
 TIP: In general, Rails encourages using resources objects instead of
@@ -2066,8 +2065,8 @@ getting up and running with Rails, feel free to consult these support
 resources:
 
 * The [Ruby on Rails Guides](index.html)
-* The [Ruby on Rails Tutorial](http://railstutorial.org/book)
-* The [Ruby on Rails mailing list](http://groups.google.com/group/rubyonrails-talk)
+* The [Ruby on Rails Tutorial](https://www.railstutorial.org/book)
+* The [Ruby on Rails mailing list](https://groups.google.com/group/rubyonrails-talk)
 * The [#rubyonrails](irc://irc.freenode.net/#rubyonrails) channel on irc.freenode.net
 
 
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 4d79b2db89..15345c94b7 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -97,7 +97,7 @@ If we want to display the properties of all the books in our view, we can do so
 <%= link_to "New book", new_book_path %>
 ```
 
-NOTE: The actual rendering is done by subclasses of `ActionView::TemplateHandlers`. This guide does not dig into that process, but it's important to know that the file extension on your view controls the choice of template handler. Beginning with Rails 2, the standard extensions are `.erb` for ERB (HTML with embedded Ruby), and `.builder` for Builder (XML generator).
+NOTE: The actual rendering is done by nested classes of the module [`ActionView::Template::Handlers`](http://api.rubyonrails.org/classes/ActionView/Template/Handlers.html). This guide does not dig into that process, but it's important to know that the file extension on your view controls the choice of template handler.
 
 ### Using `render`
 
diff --git a/guides/source/rails_on_rack.md b/guides/source/rails_on_rack.md
index 5718b9ddfc..1627205b7b 100644
--- a/guides/source/rails_on_rack.md
+++ b/guides/source/rails_on_rack.md
@@ -126,6 +126,7 @@ use ActionDispatch::ContentSecurityPolicy::Middleware
 use Rack::Head
 use Rack::ConditionalGet
 use Rack::ETag
+use Rack::TempfileReaper
 run MyApp::Application.routes
 ```
 
@@ -284,6 +285,10 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 * Sets up the flash keys. Only available if `config.action_controller.session_store` is set to a value.
 
+**`ActionDispatch::ContentSecurityPolicy::Middleware`**
+
+* Provides a DSL to configure a Content-Security-Policy header.
+
 **`Rack::Head`**
 
 * Converts HEAD requests to `GET` requests and serves them as so.
@@ -296,6 +301,10 @@ Much of Action Controller's functionality is implemented as Middlewares. The fol
 
 * Adds ETag header on all String bodies. ETags are used to validate cache.
 
+**`Rack::TempfileReaper`**
+
+* Cleans up tempfiles used to buffer multipart requests.
+
 TIP: It's possible to use any of the above middlewares in your custom Rack stack.
 
 Resources
diff --git a/guides/source/security.md b/guides/source/security.md
index ab5a5a7a31..28ddbdc26a 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -551,7 +551,7 @@ Here are some ideas how to hide honeypot fields by JavaScript and/or CSS:
 * make the elements very small or color them the same as the background of the page
 * leave the fields displayed, but tell humans to leave them blank
 
-The most simple negative CAPTCHA is one hidden honeypot field. On the server side, you will check the value of the field: If it contains any text, it must be a bot. Then, you can either ignore the post or return a positive result, but not saving the post to the database. This way the bot will be satisfied and moves on. You can do this with annoying users, too.
+The most simple negative CAPTCHA is one hidden honeypot field. On the server side, you will check the value of the field: If it contains any text, it must be a bot. Then, you can either ignore the post or return a positive result, but not saving the post to the database. This way the bot will be satisfied and moves on.
 
 You can find more sophisticated negative CAPTCHAs in Ned Batchelder's [blog post](http://nedbatchelder.com/text/stopbots.html):
 
@@ -573,18 +573,6 @@ config.filter_parameters << :password
 
 NOTE: Provided parameters will be filtered out by partial matching regular expression. Rails adds default `:password` in the appropriate initializer (`initializers/filter_parameter_logging.rb`) and cares about typical application parameters `password` and `password_confirmation`.
 
-### Good Passwords
-
-INFO: _Do you find it hard to remember all your passwords? Don't write them down, but use the initial letters of each word in an easy to remember sentence._
-
-Bruce Schneier, a security technologist, [has analyzed](http://www.schneier.com/blog/archives/2006/12/realworld_passw.html) 34,000 real-world user names and passwords from the MySpace phishing attack mentioned [below](#examples-from-the-underground). It turns out that most of the passwords are quite easy to crack. The 20 most common passwords are:
-
-password1, abc123, myspace1, password, blink182, qwerty1, ****you, 123abc, baseball1, football1, 123456, soccer, monkey1, liverpool1, princess1, jordan23, slipknot1, superman1, iloveyou1, and monkey.
-
-It is interesting that only 4% of these passwords were dictionary words and the great majority is actually alphanumeric. However, password cracker dictionaries contain a large number of today's passwords, and they try out all kinds of (alphanumerical) combinations. If an attacker knows your user name and you use a weak password, your account will be easily cracked.
-
-A good password is a long alphanumeric combination of mixed cases. As this is quite hard to remember, it is advisable to enter only the _first letters of a sentence that you can easily remember_. For example "The quick brown fox jumps over the lazy dog" will be "Tqbfjotld". Note that this is just an example, you should not use well known phrases like these, as they might appear in cracker dictionaries, too.
-
 ### Regular Expressions
 
 INFO: _A common pitfall in Ruby's regular expressions is to match the string's beginning and end by ^ and $, instead of \A and \z._
@@ -1070,7 +1058,10 @@ Every HTTP response from your Rails application receives the following default s
 config.action_dispatch.default_headers = {
   'X-Frame-Options' => 'SAMEORIGIN',
   'X-XSS-Protection' => '1; mode=block',
-  'X-Content-Type-Options' => 'nosniff'
+  'X-Content-Type-Options' => 'nosniff',
+  'X-Download-Options' => 'noopen',
+  'X-Permitted-Cross-Domain-Policies' => 'none',
+  'Referrer-Policy' => 'strict-origin-when-cross-origin'
 }
 ```
 
diff --git a/guides/source/testing.md b/guides/source/testing.md
index 0246ab844b..b9b310cbba 100644
--- a/guides/source/testing.md
+++ b/guides/source/testing.md
@@ -462,6 +462,89 @@ Rails options:
     -c, --[no-]color                 Enable color in the output
 ```
 
+Parallel Testing
+----------------
+
+Parallel testing allows you to parallelize your test suite. While forking processes is the
+default method, threading is supported as well. Running tests in parallel reduces the time it
+takes your entire test suite to run.
+
+### Parallel testing with processes
+
+The default parallelization method is to fork processes using Ruby's DRb system. The processes
+are forked based on the number of workers provided. The default is 2, but can be changed by the
+number passed to the parallelize method. Active Record automatically handles creating and
+migrating a new database for each worker to use.
+
+To enable parallelization add the following to your `test_helper.rb`:
+
+```
+class ActiveSupport::TestCase
+  parallelize(workers: 2)
+end
+```
+
+The number of workers passed is the number of times the process will be forked. You may want to
+parallelize your local test suite differently from your CI, so an environment variable is provided
+to be able to easily change the number of workers a test run should use:
+
+```
+PARALLEL_WORKERS=15 bin/rails test
+```
+
+When parallelizing tests, Active Record automatically handles creating and migrating a database for each
+process. The databases will be suffixed with the number corresponding to the worker. For example, if you
+have 2 workers the tests will create `test-database-0` and `test-database-1` respectively.
+
+If the number of workers passed is 1 or fewer the processes will not be forked and the tests will not
+be parallelized and the tests will use the original `test-database` database.
+
+Two hooks are provided, one runs when the process is forked, and one runs before the processes are closed.
+These can be useful if your app uses multiple databases or perform other tasks that depend on the number of
+workers.
+
+The `parallelize_setup` method is called right after the processes are forked. The `parallelize_teardown` metod
+is called right before the processes are closed.
+
+```
+class ActiveSupport::TestCase
+  parallelize_setup do |worker|
+    # setup databases
+  end
+
+  parallelize_teardown do |worker|
+    # cleanup database
+  end
+
+  parallelize(workers: 2)
+end
+```
+
+These methods are not needed or available when using parallel testing with threads.
+
+### Parallel testing with threads
+
+If you prefer using threads or are using JRuby, a threaded parallelization option is provided. The threaded
+parallelizer is backed by Minitest's `Parallel::Executor`.
+
+To change the parallelization method to use threads over forks put the following in your `test_helper.rb`
+
+```
+class ActiveSupport::TestCase
+  parallelize(workers: 2, with: :threads)
+end
+```
+
+Rails applications generated from JRuby will automatically include the `with: :threads` option.
+
+The number of workers passed to `parallelize` determines the number of threads the tests will use. You may
+want to parallelize your local test suite differently from your CI, so an environment variable is provided
+to be able to easily change the number of workers a test run should use:
+
+```
+PARALLEL_WORKERS=15 bin/rails test
+```
+
 The Test Database
 -----------------
 
@@ -781,6 +864,34 @@ send a POST request to create the new article in the database.
 We will be redirected back to the articles index page and there we assert
 that the text from the new article's title is on the articles index page.
 
+#### Testing for multiple screen sizes
+If you want to test for mobile sizes on top of testing for desktop,
+you can create another class that inherits from SystemTestCase and use in your
+test suite. In this example a file called `mobile_system_test_case.rb` is created
+in the `/test` directory with the following configuration.
+
+```ruby
+require "test_helper"
+
+class MobileSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :chrome, screen_size: [375, 667]
+end
+```
+To use this configuration, create a test inside `test/system` that inherits from `MobileSystemTestCase`.
+Now you can test your app using multiple different configurations.
+
+```ruby
+require "mobile_system_test_case"
+
+class PostsTest < MobileSystemTestCase
+
+  test "visiting the index" do
+    visit posts_url
+    assert_selector "h1", text: "Posts"
+  end
+end
+```
+
 #### Taking it further
 
 The beauty of system testing is that it is similar to integration testing in
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index d406b7b98b..ff7ccfd47d 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -35,6 +35,7 @@ You can find a list of all released Rails versions [here](https://rubygems.org/g
 
 Rails generally stays close to the latest released Ruby version when it's released:
 
+* Rails 6 requires Ruby 2.4.1 or newer.
 * Rails 5 requires Ruby 2.2.2 or newer.
 * Rails 4 prefers Ruby 2.0 and requires 1.9.3 or newer.
 * Rails 3.2.x is the last branch to support Ruby 1.8.7.
@@ -65,6 +66,17 @@ Overwrite /myapp/config/application.rb? (enter "h" for help) [Ynaqdh]
 
 Don't forget to review the difference, to see if there were any unexpected changes.
 
+Upgrading from Rails 5.1 to Rails 5.2
+-------------------------------------
+
+For more information on changes made to Rails 5.2 please see the [release notes](5_2_release_notes.html).
+
+### Bootsnap
+
+Rails 5.2 adds bootsnap gem in the [newly generated app's Gemfile](https://github.com/rails/rails/pull/29313).
+The `app:update` task sets it up in `boot.rb`. If you want to use it, then add it in the Gemfile,
+otherwise change the `boot.rb` to not use bootsnap.
+
 Upgrading from Rails 5.0 to Rails 5.1
 -------------------------------------
 
diff --git a/rails.gemspec b/rails.gemspec
index 4b57377871..709ce642f3 100644
--- a/rails.gemspec
+++ b/rails.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Full-stack web application framework."
   s.description = "Ruby on Rails is a full-stack web framework optimized for programmer happiness and sustainable productivity. It encourages beautiful code by favoring convention over configuration."
 
-  s.required_ruby_version     = ">= 2.2.2"
+  s.required_ruby_version     = ">= 2.4.1"
   s.required_rubygems_version = ">= 1.8.11"
 
   s.license = "MIT"
diff --git a/railties/.gitignore b/railties/.gitignore
index 80dd262d2f..c08562e016 100644
--- a/railties/.gitignore
+++ b/railties/.gitignore
@@ -1 +1,5 @@
-log/
+/log/
+/test/500.html
+/test/fixtures/tmp/
+/test/initializer/root/log/
+/tmp/
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 0658c4b55c..f1e16ec50f 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,164 +1,16 @@
-## Rails 5.2.0.beta2 (November 28, 2017) ##
+## Rails 6.0.0.alpha (Unreleased) ##
 
-*   No changes.
-
-
-## Rails 5.2.0.beta1 (November 27, 2017) ##
-
-*   Deprecate `after_bundle` callback in Rails plugin templates.
-
-    *Yuji Yaginuma*
-
-*   `rails new` and `rails plugin new` get `Active Storage` by default.
-     Add ability to skip `Active Storage` with `--skip-active-storage`
-     and do so automatically when `--skip-active-record` is used.
-
-    *bogdanvlviv*
-
-*   Gemfile for new apps: upgrade redis-rb from ~> 3.0 to 4.0.
+*   Rails 6 requires Ruby 2.4.1 or newer.
 
     *Jeremy Daer*
 
-*   Add `mini_magick` to default `Gemfile` as comment.
-
-    *Yoshiyuki Hirano*
-
-*   Derive `secret_key_base` from the app name in development and test environments.
-
-    Spares away needless secret configs.
-
-    *DHH*, *Kasper Timm Hansen*
-
-*   Support multiple versions arguments for `gem` method of Generators.
-
-    *Yoshiyuki Hirano*
-
-*   Add `--skip-yarn` option to the plugin generator.
-
-    *bogdanvlviv*
-
-*   Optimize routes indentation.
-
-    *Yoshiyuki Hirano*
-
-*   Optimize indentation for generator actions.
-
-    *Yoshiyuki Hirano*
-
-*   Skip unused components when running `bin/rails` in Rails plugin.
-
-    *Yoshiyuki Hirano*
-
-*   Add `git_source` to `Gemfile` for plugin generator.
-
-    *Yoshiyuki Hirano*
-
-*   Add `--skip-action-cable` option to the plugin generator.
-
-    *bogdanvlviv*
-
-*   Deprecate support for using a `Rails::Application` subclass to start Rails server.
-
-    *Yuji Yaginuma*
-
-*   Add `ruby x.x.x` version to `Gemfile` and create `.ruby-version`
-    root file containing the current Ruby version when new Rails applications are
-    created.
-
-    *Alberto Almagro*
-
-*   Support `-` as a platform-agnostic way to run a script from stdin with
-    `rails runner`
-
-    *Cody Cutrer*
-
-*   Add `bootsnap` to default `Gemfile`.
-
-    *Burke Libbey*
-
-*   Properly expand shortcuts for environment's name running the `console`
-    and `dbconsole` commands.
-
-    *Robin Dupret*
-
-*   Passing the environment's name as a regular argument to the
-    `rails dbconsole` and `rails console` commands is deprecated.
-    The `-e` option should be used instead.
-
-    Previously:
-
-        $ bin/rails dbconsole production
-
-    Now:
-
-        $ bin/rails dbconsole -e production
-
-    *Robin Dupret*, *Kasper Timm Hansen*
-
-*   Allow passing a custom connection name to the `rails dbconsole`
-    command when using a 3-level database configuration.
-
-        $ bin/rails dbconsole -c replica
-
-    *Robin Dupret*, *Jeremy Daer*
-
-*   Skip unused components when running `bin/rails app:update`.
-
-    If the initial app generation skipped Action Cable, Active Record etc.,
-    the update task honors those skips too.
-
-    *Yuji Yaginuma*
-
-*   Make Rails' test runner work better with minitest plugins.
-
-    By demoting the Rails test runner to just another minitest plugin —
-    and thereby not eager loading it — we can co-exist much better with
-    other minitest plugins such as pride and minitest-focus.
-
-    *Kasper Timm Hansen*
-
-*   Load environment file in `dbconsole` command.
-
-    Fixes #29717.
-
-    *Yuji Yaginuma*
-
-*   Add `rails secrets:show` command.
-
-    *Yuji Yaginuma*
-
-*   Allow mounting the same engine several times in different locations.
-
-    Fixes #20204.
-
-    *David Rodríguez*
-
-*   Clear screenshot files in `tmp:clear` task.
-
-    *Yuji Yaginuma*
-
-*   Add `railtie.rb` to the plugin generator
-
-    *Tsukuru Tanimichi*
-
-*   Deprecate `capify!` method in generators and templates.
-
-    *Yuji Yaginuma*
-
-*   Allow irb options to be passed from `rails console` command.
-
-    Fixes #28988.
-
-    *Yuji Yaginuma*
-
-*   Added a shared section to `config/database.yml` that will be loaded for all environments.
+*   Fix minitest rails plugin.
 
-    *Pierre Schambacher*
+    The custom reporters are added only if needed.
 
-*   Namespace error pages' CSS selectors to stop the styles from bleeding into other pages
-    when using Turbolinks.
+    This will fix conflicts with others plugins.
 
-    *Jan Krutisch*
+    *Kevin Robatel*
 
 
-Please check [5-1-stable](https://github.com/rails/rails/blob/5-1-stable/railties/CHANGELOG.md) for previous changes.
+Please check [5-2-stable](https://github.com/rails/rails/blob/5-2-stable/railties/CHANGELOG.md) for previous changes.
diff --git a/railties/lib/minitest/rails_plugin.rb b/railties/lib/minitest/rails_plugin.rb
index 6901b0bbc8..7193abbc33 100644
--- a/railties/lib/minitest/rails_plugin.rb
+++ b/railties/lib/minitest/rails_plugin.rb
@@ -43,10 +43,15 @@ module Minitest
       Minitest.backtrace_filter = ::Rails.backtrace_cleaner if ::Rails.respond_to?(:backtrace_cleaner)
     end
 
+    # Suppress summary reports when outputting inline rerun snippets.
+    if reporter.reporters.reject! { |reporter| reporter.kind_of?(SummaryReporter) }
+      reporter << SuppressedSummaryReporter.new(options[:io], options)
+    end
+
     # Replace progress reporter for colors.
-    reporter.reporters.delete_if { |reporter| reporter.kind_of?(SummaryReporter) || reporter.kind_of?(ProgressReporter) }
-    reporter << SuppressedSummaryReporter.new(options[:io], options)
-    reporter << ::Rails::TestUnitReporter.new(options[:io], options)
+    if reporter.reporters.reject! { |reporter| reporter.kind_of?(ProgressReporter) }
+      reporter << ::Rails::TestUnitReporter.new(options[:io], options)
+    end
   end
 
   # Backwardscompatibility with Rails 5.0 generated plugin test scripts
diff --git a/railties/lib/rails/application.rb b/railties/lib/rails/application.rb
index a200a1005c..a9dee10981 100644
--- a/railties/lib/rails/application.rb
+++ b/railties/lib/rails/application.rb
@@ -268,7 +268,8 @@ module Rails
           "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest,
           "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations,
           "action_dispatch.content_security_policy" => config.content_security_policy,
-          "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only
+          "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only,
+          "action_dispatch.content_security_policy_nonce_generator" => config.content_security_policy_nonce_generator
         )
       end
     end
diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index f02aef94e0..b42ffe50d8 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -17,47 +17,49 @@ module Rails
                     :session_options, :time_zone, :reload_classes_only_on_change,
                     :beginning_of_week, :filter_redirect, :x, :enable_dependency_loading,
                     :read_encrypted_secrets, :log_level, :content_security_policy_report_only,
-                    :require_master_key
+                    :content_security_policy_nonce_generator, :require_master_key
 
-      attr_reader :encoding, :api_only
+      attr_reader :encoding, :api_only, :loaded_config_version
 
       def initialize(*)
         super
-        self.encoding                        = Encoding::UTF_8
-        @allow_concurrency                   = nil
-        @consider_all_requests_local         = false
-        @filter_parameters                   = []
-        @filter_redirect                     = []
-        @helpers_paths                       = []
-        @public_file_server                  = ActiveSupport::OrderedOptions.new
-        @public_file_server.enabled          = true
-        @public_file_server.index_name       = "index"
-        @force_ssl                           = false
-        @ssl_options                         = {}
-        @session_store                       = nil
-        @time_zone                           = "UTC"
-        @beginning_of_week                   = :monday
-        @log_level                           = :debug
-        @generators                          = app_generators
-        @cache_store                         = [ :file_store, "#{root}/tmp/cache/" ]
-        @railties_order                      = [:all]
-        @relative_url_root                   = ENV["RAILS_RELATIVE_URL_ROOT"]
-        @reload_classes_only_on_change       = true
-        @file_watcher                        = ActiveSupport::FileUpdateChecker
-        @exceptions_app                      = nil
-        @autoflush_log                       = true
-        @log_formatter                       = ActiveSupport::Logger::SimpleFormatter.new
-        @eager_load                          = nil
-        @secret_token                        = nil
-        @secret_key_base                     = nil
-        @api_only                            = false
-        @debug_exception_response_format     = nil
-        @x                                   = Custom.new
-        @enable_dependency_loading           = false
-        @read_encrypted_secrets              = false
-        @content_security_policy             = nil
-        @content_security_policy_report_only = false
-        @require_master_key                  = false
+        self.encoding                            = Encoding::UTF_8
+        @allow_concurrency                       = nil
+        @consider_all_requests_local             = false
+        @filter_parameters                       = []
+        @filter_redirect                         = []
+        @helpers_paths                           = []
+        @public_file_server                      = ActiveSupport::OrderedOptions.new
+        @public_file_server.enabled              = true
+        @public_file_server.index_name           = "index"
+        @force_ssl                               = false
+        @ssl_options                             = {}
+        @session_store                           = nil
+        @time_zone                               = "UTC"
+        @beginning_of_week                       = :monday
+        @log_level                               = :debug
+        @generators                              = app_generators
+        @cache_store                             = [ :file_store, "#{root}/tmp/cache/" ]
+        @railties_order                          = [:all]
+        @relative_url_root                       = ENV["RAILS_RELATIVE_URL_ROOT"]
+        @reload_classes_only_on_change           = true
+        @file_watcher                            = ActiveSupport::FileUpdateChecker
+        @exceptions_app                          = nil
+        @autoflush_log                           = true
+        @log_formatter                           = ActiveSupport::Logger::SimpleFormatter.new
+        @eager_load                              = nil
+        @secret_token                            = nil
+        @secret_key_base                         = nil
+        @api_only                                = false
+        @debug_exception_response_format         = nil
+        @x                                       = Custom.new
+        @enable_dependency_loading               = false
+        @read_encrypted_secrets                  = false
+        @content_security_policy                 = nil
+        @content_security_policy_report_only     = false
+        @content_security_policy_nonce_generator = nil
+        @require_master_key                      = false
+        @loaded_config_version                   = nil
       end
 
       def load_defaults(target_version)
@@ -112,9 +114,14 @@ module Rails
           if respond_to?(:action_view)
             action_view.form_with_generates_ids = true
           end
+        when "6.0"
+          load_defaults "5.2"
+
         else
           raise "Unknown version #{target_version.to_s.inspect}"
         end
+
+        @loaded_config_version = target_version
       end
 
       def encoding=(value)
@@ -235,7 +242,11 @@ module Rails
       end
 
       def content_security_policy(&block)
-        @content_security_policy ||= ActionDispatch::ContentSecurityPolicy.new(&block)
+        if block_given?
+          @content_security_policy = ActionDispatch::ContentSecurityPolicy.new(&block)
+        else
+          @content_security_policy
+        end
       end
 
       class Custom #:nodoc:
diff --git a/railties/lib/rails/application/default_middleware_stack.rb b/railties/lib/rails/application/default_middleware_stack.rb
index 0e79ba7da0..433a7ab41f 100644
--- a/railties/lib/rails/application/default_middleware_stack.rb
+++ b/railties/lib/rails/application/default_middleware_stack.rb
@@ -70,6 +70,8 @@ module Rails
           middleware.use ::Rack::Head
           middleware.use ::Rack::ConditionalGet
           middleware.use ::Rack::ETag, "no-cache"
+
+          middleware.use ::Rack::TempfileReaper unless config.api_only
         end
       end
 
diff --git a/railties/lib/rails/command.rb b/railties/lib/rails/command.rb
index 812e846837..078e9f937f 100644
--- a/railties/lib/rails/command.rb
+++ b/railties/lib/rails/command.rb
@@ -4,7 +4,6 @@ require "active_support"
 require "active_support/dependencies/autoload"
 require "active_support/core_ext/enumerable"
 require "active_support/core_ext/object/blank"
-require "active_support/core_ext/hash/transform_values"
 
 require "thor"
 
diff --git a/railties/lib/rails/commands/credentials/credentials_command.rb b/railties/lib/rails/commands/credentials/credentials_command.rb
index 385d3976da..fa54c0362a 100644
--- a/railties/lib/rails/commands/credentials/credentials_command.rb
+++ b/railties/lib/rails/commands/credentials/credentials_command.rb
@@ -20,7 +20,7 @@ module Rails
         require_application_and_environment!
 
         ensure_editor_available(command: "bin/rails credentials:edit") || (return)
-        ensure_master_key_has_been_added
+        ensure_master_key_has_been_added if Rails.application.credentials.key.nil?
         ensure_credentials_have_been_added
 
         catch_editing_exceptions do
diff --git a/railties/lib/rails/commands/encrypted/encrypted_command.rb b/railties/lib/rails/commands/encrypted/encrypted_command.rb
index 912c453f09..3bc8f76ce4 100644
--- a/railties/lib/rails/commands/encrypted/encrypted_command.rb
+++ b/railties/lib/rails/commands/encrypted/encrypted_command.rb
@@ -21,9 +21,10 @@ module Rails
 
       def edit(file_path)
         require_application_and_environment!
+        encrypted = Rails.application.encrypted(file_path, key_path: options[:key])
 
         ensure_editor_available(command: "bin/rails encrypted:edit") || (return)
-        ensure_encryption_key_has_been_added(options[:key])
+        ensure_encryption_key_has_been_added(options[:key]) if encrypted.key.nil?
         ensure_encrypted_file_has_been_added(file_path, options[:key])
 
         catch_editing_exceptions do
diff --git a/railties/lib/rails/gem_version.rb b/railties/lib/rails/gem_version.rb
index 2cc861a1bd..54bfbdd516 100644
--- a/railties/lib/rails/gem_version.rb
+++ b/railties/lib/rails/gem_version.rb
@@ -7,10 +7,10 @@ module Rails
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index 6c9c109f17..6a7175c02b 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -218,6 +218,9 @@ module Rails
         rails.delete("app")
         rails.delete("plugin")
         rails.delete("encrypted_secrets")
+        rails.delete("encrypted_file")
+        rails.delete("encryption_key_file")
+        rails.delete("master_key")
         rails.delete("credentials")
 
         hidden_namespaces.each { |n| groups.delete(n.to_s) }
diff --git a/railties/lib/rails/generators/actions.rb b/railties/lib/rails/generators/actions.rb
index 3362bf629a..d85bbfb03e 100644
--- a/railties/lib/rails/generators/actions.rb
+++ b/railties/lib/rails/generators/actions.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/string/strip"
+
 module Rails
   module Generators
     module Actions
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index e152a95fd3..e1889979d7 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -2,7 +2,6 @@
 
 require "fileutils"
 require "digest/md5"
-require "active_support/core_ext/string/strip"
 require "rails/version" unless defined?(Rails::VERSION)
 require "open-uri"
 require "uri"
@@ -315,11 +314,13 @@ module Rails
 
       def convert_database_option_for_jruby
         if defined?(JRUBY_VERSION)
-          case options[:database]
-          when "postgresql" then options[:database].replace "jdbcpostgresql"
-          when "mysql"      then options[:database].replace "jdbcmysql"
-          when "sqlite3"    then options[:database].replace "jdbcsqlite3"
+          opt = options.dup
+          case opt[:database]
+          when "postgresql" then opt[:database] = "jdbcpostgresql"
+          when "mysql"      then opt[:database] = "jdbcmysql"
+          when "sqlite3"    then opt[:database] = "jdbcsqlite3"
           end
+          self.options = opt.freeze
         end
       end
 
diff --git a/railties/lib/rails/generators/generated_attribute.rb b/railties/lib/rails/generators/generated_attribute.rb
index 2728459968..f7fd30a5fb 100644
--- a/railties/lib/rails/generators/generated_attribute.rb
+++ b/railties/lib/rails/generators/generated_attribute.rb
@@ -75,7 +75,7 @@ module Rails
                         when :date                 then :date_select
                         when :text                 then :text_area
                         when :boolean              then :check_box
-          else
+                        else
                           :text_field
         end
       end
@@ -91,7 +91,7 @@ module Rails
                      when :text                        then "MyText"
                      when :boolean                     then false
                      when :references, :belongs_to     then nil
-          else
+                     else
                        ""
         end
       end
diff --git a/railties/lib/rails/generators/named_base.rb b/railties/lib/rails/generators/named_base.rb
index 98fcc95964..d6732f8ff1 100644
--- a/railties/lib/rails/generators/named_base.rb
+++ b/railties/lib/rails/generators/named_base.rb
@@ -31,12 +31,8 @@ module Rails
         end
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-        attr_reader :file_name
-
       private
+        attr_reader :file_name
 
         # FIXME: We are avoiding to use alias because a bug on thor that make
         # this method public and add it to the task list.
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index fd9da7803f..5ee9ae05e3 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -130,6 +130,8 @@ module Rails
       assets_config_exist            = File.exist?("config/initializers/assets.rb")
       csp_config_exist               = File.exist?("config/initializers/content_security_policy.rb")
 
+      @config_target_version = Rails.application.config.loaded_config_version || "5.0"
+
       config
 
       unless cookie_serializer_config_exist
@@ -167,7 +169,7 @@ module Rails
       return if options[:pretend] || options[:dummy_app]
 
       require "rails/generators/rails/master_key/master_key_generator"
-      master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet])
+      master_key_generator = Rails::Generators::MasterKeyGenerator.new([], quiet: options[:quiet], force: options[:force])
       master_key_generator.add_master_key_file_silently
       master_key_generator.ignore_master_key_file_silently
     end
@@ -233,6 +235,10 @@ module Rails
     def vendor
       empty_directory_with_keep_file "vendor"
     end
+
+    def config_target_version
+      defined?(@config_target_version) ? @config_target_version : Rails::VERSION::STRING.to_f
+    end
   end
 
   module Generators
@@ -242,7 +248,7 @@ module Rails
     RESERVED_NAMES = %w[application destroy plugin runner test]
 
     class AppGenerator < AppBase # :nodoc:
-      WEBPACKS = %w( react vue angular elm )
+      WEBPACKS = %w( react vue angular elm stimulus )
 
       add_shared_options_for "application"
 
@@ -383,9 +389,13 @@ module Rails
         end
       end
 
-      def delete_application_layout_file_if_api_option
+      def delete_app_views_if_api_option
         if options[:api]
-          remove_file "app/views/layouts/application.html.erb"
+          if options[:skip_action_mailer]
+            remove_dir "app/views"
+          else
+            remove_file "app/views/layouts/application.html.erb"
+          end
         end
       end
 
diff --git a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
index 5460155b3e..ef715f1368 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
@@ -3,6 +3,7 @@
   <head>
     <title><%= camelized %></title>
     <%%= csrf_meta_tags %>
+    <%%= csp_meta_tag %>
 
     <%- if options[:skip_javascript] -%>
     <%%= stylesheet_link_tag    'application', media: 'all' %>
diff --git a/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
index b4e4d95286..90ddcc520e 100644
--- a/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
+++ b/railties/lib/rails/generators/rails/app/templates/bin/yarn.tt
@@ -1,7 +1,7 @@
 APP_ROOT = File.expand_path('..', __dir__)
 Dir.chdir(APP_ROOT) do
   begin
-    exec "yarnpkg #{ARGV.join(' ')}"
+    exec "yarnpkg", *ARGV
   rescue Errno::ENOENT
     $stderr.puts "Yarn executable was not detected in the system."
     $stderr.puts "Download Yarn at https://yarnpkg.com/en/docs/install"
diff --git a/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
index d1a09f9c3c..9a427113c7 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt
@@ -24,7 +24,7 @@ Bundler.require(*Rails.groups)
 module <%= app_const_base %>
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    config.load_defaults <%= Rails::VERSION::STRING.to_f %>
+    config.load_defaults <%= build(:config_target_version) %>
 
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration can go into files in config/initializers
diff --git a/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
index 720d36a2a4..42d46b8175 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/boot.rb.tt
@@ -4,7 +4,3 @@ require 'bundler/setup' # Set up gems listed in the Gemfile.
 <% if depend_on_bootsnap? -%>
 require 'bootsnap/setup' # Speed up boot time by caching expensive operations.
 <%- end -%>
-
-if %w[s server c console].any? { |a| ARGV.include?(a) }
-  puts "=> Booting Rails"
-end
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
index 4c0f36db98..926326b5bb 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
@@ -34,8 +34,6 @@ Rails.application.configure do
   # Do not fallback to assets pipeline if a precompiled asset is missed.
   config.assets.compile = false
 
-  # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb
-
   <%- end -%>
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.action_controller.asset_host = 'http://assets.example.com'
diff --git a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
index c82324ae4d..d3bcaa5ec8 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/initializers/content_security_policy.rb.tt
@@ -4,17 +4,20 @@
 # For further information see the following documentation
 # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
 
-Rails.application.config.content_security_policy do |policy|
-  policy.default_src :self, :https
-  policy.font_src    :self, :https, :data
-  policy.img_src     :self, :https, :data
-  policy.object_src  :none
-  policy.script_src  :self, :https, :unsafe_inline
-  policy.style_src   :self, :https, :unsafe_inline
+# Rails.application.config.content_security_policy do |policy|
+#   policy.default_src :self, :https
+#   policy.font_src    :self, :https, :data
+#   policy.img_src     :self, :https, :data
+#   policy.object_src  :none
+#   policy.script_src  :self, :https
+#   policy.style_src   :self, :https
 
-  # Specify URI for violation reports
-  # policy.report_uri "/csp-violation-report-endpoint"
-end
+#   # Specify URI for violation reports
+#   # policy.report_uri "/csp-violation-report-endpoint"
+# end
+
+# If you are using UJS then enable automatic nonce generation
+# Rails.application.config.content_security_policy_nonce_generator = -> request { SecureRandom.base64(16) }
 
 # Report CSP violations to a specified URI
 # For further information see the following documentation:
diff --git a/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
index fac165a24d..1c0cde0b09 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt
@@ -1,12 +1,10 @@
 test:
   service: Disk
   root: <%%= Rails.root.join("tmp/storage") %>
-  host: http://localhost:3000
 
 local:
   service: Disk
   root: <%%= Rails.root.join("storage") %>
-  host: http://localhost:3000
 
 # Use rails credentials:edit to set the AWS secrets (as aws:access_key_id|secret_access_key)
 # amazon:
diff --git a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
index 52d68cc77c..c918b57eca 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
@@ -3,6 +3,13 @@ require_relative '../config/environment'
 require 'rails/test_help'
 
 class ActiveSupport::TestCase
+  # Run tests in parallel with specified workers
+<% if defined?(JRUBY_VERSION) -%>
+  parallelize(workers: 2, with: :threads)
+<%- else -%>
+  parallelize(workers: 2)
+<% end -%>
+
 <% unless options[:skip_active_record] -%>
   # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
   fixtures :all
diff --git a/railties/lib/rails/generators/rails/controller/controller_generator.rb b/railties/lib/rails/generators/rails/controller/controller_generator.rb
index 6d45d6e8f8..6e2495d45f 100644
--- a/railties/lib/rails/generators/rails/controller/controller_generator.rb
+++ b/railties/lib/rails/generators/rails/controller/controller_generator.rb
@@ -16,6 +16,7 @@ module Rails
 
       def add_routes
         return if options[:skip_routes]
+        return if actions.empty?
         route generate_routing_code
       end
 
diff --git a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
index 9103b1122e..719e0c1e4c 100644
--- a/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
+++ b/railties/lib/rails/generators/rails/credentials/credentials_generator.rb
@@ -6,7 +6,7 @@ require "active_support/encrypted_configuration"
 
 module Rails
   module Generators
-    class CredentialsGenerator < Base
+    class CredentialsGenerator < Base # :nodoc:
       def add_credentials_file
         unless credentials.content_path.exist?
           template = credentials_template
@@ -42,9 +42,14 @@ module Rails
         end
 
         def credentials_template
-          "# aws:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n" +
-          "# Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.\n" +
-          "secret_key_base: #{SecureRandom.hex(64)}"
+          <<~YAML
+            # aws:
+            #   access_key_id: 123
+            #   secret_access_key: 345
+
+            # Used as the base secret for all MessageVerifiers in Rails, including the one protecting cookies.
+            secret_key_base: #{SecureRandom.hex(64)}
+          YAML
         end
     end
   end
diff --git a/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
index 4ce2fc1d86..867e28c6db 100644
--- a/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
+++ b/railties/lib/rails/generators/rails/encrypted_file/encrypted_file_generator.rb
@@ -5,23 +5,7 @@ require "active_support/encrypted_file"
 
 module Rails
   module Generators
-    class EncryptedFileGenerator < Base
-      def add_encrypted_file(file_path, key_path)
-        unless File.exist?(file_path)
-          say "Adding #{file_path} to store encrypted content."
-          say ""
-          say "The following content has been encrypted with the encryption key:"
-          say ""
-          say template, :on_green
-          say ""
-
-          add_encrypted_file_silently(file_path, key_path)
-
-          say "You can edit encrypted file with `bin/rails encrypted:edit #{file_path}`."
-          say ""
-        end
-      end
-
+    class EncryptedFileGenerator < Base # :nodoc:
       def add_encrypted_file_silently(file_path, key_path, template = encrypted_file_template)
         unless File.exist?(file_path)
           setup = { content_path: file_path, key_path: key_path, env_key: "RAILS_MASTER_KEY", raise_if_missing_key: true }
@@ -31,7 +15,12 @@ module Rails
 
       private
         def encrypted_file_template
-          "# aws:\n#  access_key_id: 123\n#  secret_access_key: 345\n\n"
+          <<~YAML
+            # aws:
+            #   access_key_id: 123
+            #   secret_access_key: 345
+
+          YAML
         end
     end
   end
diff --git a/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
index a396a9661f..90068c678d 100644
--- a/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
+++ b/railties/lib/rails/generators/rails/encryption_key_file/encryption_key_file_generator.rb
@@ -6,7 +6,7 @@ require "active_support/encrypted_file"
 
 module Rails
   module Generators
-    class EncryptionKeyFileGenerator < Base
+    class EncryptionKeyFileGenerator < Base # :nodoc:
       def add_key_file(key_path)
         key_path = Pathname.new(key_path)
 
diff --git a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
index 7f57340c11..21664ea86d 100644
--- a/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
+++ b/railties/lib/rails/generators/rails/master_key/master_key_generator.rb
@@ -7,7 +7,7 @@ require "active_support/encrypted_file"
 
 module Rails
   module Generators
-    class MasterKeyGenerator < Base
+    class MasterKeyGenerator < Base # :nodoc:
       MASTER_KEY_PATH = Pathname.new("config/master.key")
 
       def add_master_key_file
@@ -27,7 +27,9 @@ module Rails
       end
 
       def add_master_key_file_silently(key = nil)
-        key_file_generator.add_key_file_silently(MASTER_KEY_PATH, key)
+        unless MASTER_KEY_PATH.exist?
+          key_file_generator.add_key_file_silently(MASTER_KEY_PATH, key)
+        end
       end
 
       def ignore_master_key_file
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
index abbacd9bec..b86ef0f2f8 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/controllers/%namespaced_name%/application_controller.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationController < ActionController::#{api? ? "API" : "Base"}
     #{ api? ? '# ' : '' }protect_from_forgery with: :exception
   end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
index 25d692732d..be078f36de 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/helpers/%namespaced_name%/application_helper.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   module ApplicationHelper
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
index bad1ff2d16..846863bc13 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/jobs/%namespaced_name%/application_job.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationJob < ActiveJob::Base
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
index 09aac13f42..246e274348 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/mailers/%namespaced_name%/application_mailer.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationMailer < ActionMailer::Base
     default from: 'from@example.com'
     layout 'mailer'
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
index 8aa3de78f1..21465278be 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/models/%namespaced_name%/application_record.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class ApplicationRecord < ActiveRecord::Base
     self.abstract_class = true
   end
diff --git a/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt b/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
index 6bc480161d..6e54a1ce9d 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/app/views/layouts/%namespaced_name%/application.html.erb.tt
@@ -2,9 +2,13 @@
 <html>
 <head>
   <title><%= humanized %></title>
+  <%%= csrf_meta_tags %>
+  <%%= csp_meta_tag %>
+
   <%%= stylesheet_link_tag    "<%= namespaced_name %>/application", media: "all" %>
+  <%- unless options[:skip_javascript] -%>
   <%%= javascript_include_tag "<%= namespaced_name %>/application" %>
-  <%%= csrf_meta_tags %>
+  <%- end -%>
 </head>
 <body>
 
diff --git a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
index b3264509fc..ee8e469da2 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/bin/rails.tt
@@ -19,10 +19,10 @@ require "rails"
 require "active_model/railtie"
 require "active_job/railtie"
 <%= comment_if :skip_active_record %>require "active_record/railtie"
+<%= comment_if :skip_active_storage %>require "active_storage/engine"
 require "action_controller/railtie"
 <%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
 require "action_view/railtie"
-require "active_storage/engine"
 <%= comment_if :skip_action_cable %>require "action_cable/engine"
 <%= comment_if :skip_sprockets %>require "sprockets/railtie"
 <%= comment_if :skip_test %>require "rails/test_unit/railtie"
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
index 8938770fc4..4ec1804940 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/engine.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class Engine < ::Rails::Engine
   #{mountable? ? '  isolate_namespace ' + camelized_modules : ' '}
   #{api? ? "  config.generators.api_only = true" : ' '}
diff --git a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
index 7bdf4ee5fb..b853fabcc3 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/lib/%namespaced_name%/railtie.rb.tt
@@ -1,4 +1,4 @@
-<%= wrap_in_modules <<-rb.strip_heredoc
+<%= wrap_in_modules <<~rb
   class Railtie < ::Rails::Railtie
   end
 rb
diff --git a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
index f3d80c87f5..51049826bf 100644
--- a/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
+++ b/railties/lib/rails/generators/rails/plugin/templates/rails/javascripts.js.tt
@@ -10,6 +10,7 @@
 // Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
 // about supported directives.
 //
+//= require rails-ujs
 <% unless skip_active_storage? -%>
 //= require activestorage
 <% end -%>
diff --git a/railties/lib/rails/generators/resource_helpers.rb b/railties/lib/rails/generators/resource_helpers.rb
index a146a8fda6..5675faff70 100644
--- a/railties/lib/rails/generators/resource_helpers.rb
+++ b/railties/lib/rails/generators/resource_helpers.rb
@@ -25,13 +25,8 @@ module Rails
         assign_controller_names!(controller_name.pluralize)
       end
 
-      # TODO Change this to private once we've dropped Ruby 2.2 support.
-      # Workaround for Ruby 2.2 "private attribute?" warning.
-      protected
-
-        attr_reader :controller_name, :controller_file_name
-
       private
+        attr_reader :controller_name, :controller_file_name
 
         def controller_class_path
           if options[:model_name]
diff --git a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
index b6c13b41ae..e2e8b18eab 100644
--- a/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
+++ b/railties/lib/rails/generators/test_unit/scaffold/scaffold_generator.rb
@@ -23,7 +23,7 @@ module TestUnit # :nodoc:
         template template_file,
                  File.join("test/controllers", controller_class_path, "#{controller_file_name}_controller_test.rb")
 
-        unless options.api? || options[:system_tests].nil?
+        if !options.api? && options[:system_tests]
           template "system_test.rb", File.join("test/system", class_path, "#{file_name.pluralize}_test.rb")
         end
       end
diff --git a/railties/lib/rails/info.rb b/railties/lib/rails/info.rb
index d8f361f524..d5c9973c6b 100644
--- a/railties/lib/rails/info.rb
+++ b/railties/lib/rails/info.rb
@@ -99,7 +99,7 @@ module Rails
     end
 
     property "Database schema version" do
-      ActiveRecord::Migrator.current_version rescue nil
+      ActiveRecord::Base.connection.migration_context.current_version rescue nil
     end
   end
 end
diff --git a/railties/lib/rails/mailers_controller.rb b/railties/lib/rails/mailers_controller.rb
index 66636e5d6b..0b0e802358 100644
--- a/railties/lib/rails/mailers_controller.rb
+++ b/railties/lib/rails/mailers_controller.rb
@@ -6,9 +6,9 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
   prepend_view_path ActionDispatch::DebugExceptions::RESCUES_TEMPLATE_PATH
 
   before_action :require_local!, unless: :show_previews?
-  before_action :find_preview, only: :preview
+  before_action :find_preview, :set_locale, only: :preview
 
-  helper_method :part_query
+  helper_method :part_query, :locale_query
 
   def index
     @previews = ActionMailer::Preview.all
@@ -84,4 +84,12 @@ class Rails::MailersController < Rails::ApplicationController # :nodoc:
     def part_query(mime_type)
       request.query_parameters.merge(part: mime_type).to_query
     end
+
+    def locale_query(locale)
+      request.query_parameters.merge(locale: locale).to_query
+    end
+
+    def set_locale
+      I18n.locale = params[:locale] || I18n.default_locale
+    end
 end
diff --git a/railties/lib/rails/ruby_version_check.rb b/railties/lib/rails/ruby_version_check.rb
index 76b6b80d28..f8d3311156 100644
--- a/railties/lib/rails/ruby_version_check.rb
+++ b/railties/lib/rails/ruby_version_check.rb
@@ -1,15 +1,15 @@
 # frozen_string_literal: true
 
-if RUBY_VERSION < "2.2.2" && RUBY_ENGINE == "ruby"
+if RUBY_VERSION < "2.4.1" && RUBY_ENGINE == "ruby"
   desc = defined?(RUBY_DESCRIPTION) ? RUBY_DESCRIPTION : "ruby #{RUBY_VERSION} (#{RUBY_RELEASE_DATE})"
   abort <<-end_message
 
-    Rails 5 requires Ruby 2.2.2 or newer.
+    Rails 6 requires Ruby 2.4.1 or newer.
 
     You're running
       #{desc}
 
-    Please upgrade to Ruby 2.2.2 or newer to continue.
+    Please upgrade to Ruby 2.4.1 or newer to continue.
 
   end_message
 end
diff --git a/railties/lib/rails/secrets.rb b/railties/lib/rails/secrets.rb
index 30e3478c9b..747cf31d7a 100644
--- a/railties/lib/rails/secrets.rb
+++ b/railties/lib/rails/secrets.rb
@@ -2,7 +2,6 @@
 
 require "yaml"
 require "active_support/message_encryptor"
-require "active_support/core_ext/string/strip"
 
 module Rails
   # Greatly inspired by Ara T. Howard's magnificent sekrets gem. 😘
diff --git a/railties/lib/rails/templates/rails/mailers/email.html.erb b/railties/lib/rails/templates/rails/mailers/email.html.erb
index 89c1129f90..2a41c29602 100644
--- a/railties/lib/rails/templates/rails/mailers/email.html.erb
+++ b/railties/lib/rails/templates/rails/mailers/email.html.erb
@@ -95,11 +95,25 @@
       </dd>
     <% end %>
 
+    <dt>Format:</dt>
     <% if @email.multipart? %>
       <dd>
-        <select onchange="formatChanged(this);">
-          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="?<%= part_query('text/html') %>">View as HTML email</option>
-          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="?<%= part_query('text/plain') %>">View as plain-text email</option>
+        <select id="part" onchange="refreshBody();">
+          <option <%= request.format == Mime[:html] ? 'selected' : '' %> value="<%= part_query('text/html') %>">View as HTML email</option>
+          <option <%= request.format == Mime[:text] ? 'selected' : '' %> value="<%= part_query('text/plain') %>">View as plain-text email</option>
+        </select>
+      </dd>
+    <% else %>
+      <dd id="mime_type" data-mime-type="<%= part_query(@email.mime_type) %>"><%= @email.mime_type == 'text/html' ? 'HTML email' : 'plain-text email' %></dd>
+    <% end %>
+
+    <% if I18n.available_locales.count > 1 %>
+      <dt>Locale:</dt>
+      <dd>
+        <select id="locale" onchange="refreshBody();">
+          <% I18n.available_locales.each do |locale| %>
+            <option <%= I18n.locale == locale ? 'selected' : '' %> value="<%= locale_query(locale) %>"><%= locale %></option>
+          <% end %>
         </select>
       </dd>
     <% end %>
@@ -116,15 +130,27 @@
 <% end %>
 
 <script>
-  function formatChanged(form) {
-    var part_name = form.options[form.selectedIndex].value
-    var iframe =document.getElementsByName('messageBody')[0];
-    iframe.contentWindow.location.replace(part_name);
+  function refreshBody() {
+    var part_select = document.querySelector('select#part');
+    var locale_select = document.querySelector('select#locale');
+    var iframe = document.getElementsByName('messageBody')[0];
+    var part_param = part_select ?
+      part_select.options[part_select.selectedIndex].value :
+      document.querySelector('#mime_type').dataset.mimeType;
+    var locale_param = locale_select ? locale_select.options[locale_select.selectedIndex].value : null;
+    var fresh_location;
+    if (locale_param) {
+      fresh_location = '?' + part_param + '&' + locale_param;
+    } else {
+      fresh_location = '?' + part_param;
+    }
+    iframe.contentWindow.location = fresh_location;
 
     if (history.replaceState) {
-      var url    = location.pathname.replace(/\.(txt|html)$/, '');
-      var format = /html/.test(part_name) ? '.html' : '.txt';
-      window.history.replaceState({}, '', url + format);
+      var url = location.pathname.replace(/\.(txt|html)$/, '');
+      var format = /html/.test(part_param) ? '.html' : '.txt';
+      var state_to_replace = locale_param ? (url + format + '?' + locale_param) : (url + format);
+      window.history.replaceState({}, '', state_to_replace);
     }
   }
 </script>
diff --git a/railties/lib/rails/test_help.rb b/railties/lib/rails/test_help.rb
index 76c28ac85e..4bd7d74b04 100644
--- a/railties/lib/rails/test_help.rb
+++ b/railties/lib/rails/test_help.rb
@@ -22,6 +22,7 @@ if defined?(ActiveRecord::Base)
 
   module ActiveSupport
     class TestCase
+      include ActiveRecord::TestDatabases
       include ActiveRecord::TestFixtures
       self.fixture_path = "#{Rails.root}/test/fixtures/"
       self.file_fixture_path = fixture_path + "files"
diff --git a/railties/railties.gemspec b/railties/railties.gemspec
index 4c665cd546..1df8b1fe39 100644
--- a/railties/railties.gemspec
+++ b/railties/railties.gemspec
@@ -9,7 +9,7 @@ Gem::Specification.new do |s|
   s.summary     = "Tools for creating, working with, and running Rails applications."
   s.description = "Rails internals: application bootup, plugins, generators, and rake tasks."
 
-  s.required_ruby_version = ">= 2.2.2"
+  s.required_ruby_version = ">= 2.4.1"
 
   s.license = "MIT"
 
diff --git a/railties/test/application/configuration/custom_test.rb b/railties/test/application/configuration/custom_test.rb
index 05b17b4a7a..608bc2fbe3 100644
--- a/railties/test/application/configuration/custom_test.rb
+++ b/railties/test/application/configuration/custom_test.rb
@@ -33,7 +33,7 @@ module ApplicationTests
         assert_nil x.i_do_not_exist.zomg
 
         # test that custom configuration responds to all messages
-        assert_equal true, x.respond_to?(:i_do_not_exist)
+        assert_respond_to x, :i_do_not_exist
         assert_kind_of Method, x.method(:i_do_not_exist)
         assert_kind_of ActiveSupport::OrderedOptions, x.i_do_not_exist
       end
diff --git a/railties/test/application/configuration_test.rb b/railties/test/application/configuration_test.rb
index 5f932f38db..caadae3136 100644
--- a/railties/test/application/configuration_test.rb
+++ b/railties/test/application/configuration_test.rb
@@ -94,7 +94,7 @@ module ApplicationTests
 
       with_rails_env "development" do
         app "development"
-        assert Rails.application.config.log_tags.blank?
+        assert_predicate Rails.application.config.log_tags, :blank?
       end
     end
 
@@ -1419,11 +1419,11 @@ module ApplicationTests
     test "Rails.application#env_config exists and include some existing parameters" do
       make_basic_app
 
-      assert_equal      app.env_config["action_dispatch.parameter_filter"],  app.config.filter_parameters
-      assert_equal      app.env_config["action_dispatch.show_exceptions"],   app.config.action_dispatch.show_exceptions
-      assert_equal      app.env_config["action_dispatch.logger"],            Rails.logger
-      assert_equal      app.env_config["action_dispatch.backtrace_cleaner"], Rails.backtrace_cleaner
-      assert_equal      app.env_config["action_dispatch.key_generator"],     Rails.application.key_generator
+      assert_equal app.env_config["action_dispatch.parameter_filter"],  app.config.filter_parameters
+      assert_equal app.env_config["action_dispatch.show_exceptions"],   app.config.action_dispatch.show_exceptions
+      assert_equal app.env_config["action_dispatch.logger"],            Rails.logger
+      assert_equal app.env_config["action_dispatch.backtrace_cleaner"], Rails.backtrace_cleaner
+      assert_equal app.env_config["action_dispatch.key_generator"],     Rails.application.key_generator
     end
 
     test "config.colorize_logging default is true" do
@@ -1478,7 +1478,7 @@ module ApplicationTests
     test "respond_to? accepts include_private" do
       make_basic_app
 
-      assert_not Rails.configuration.respond_to?(:method_missing)
+      assert_not_respond_to Rails.configuration, :method_missing
       assert Rails.configuration.respond_to?(:method_missing, true)
     end
 
@@ -1831,7 +1831,7 @@ module ApplicationTests
 
     test "api_only is false by default" do
       app "development"
-      refute Rails.application.config.api_only
+      assert_not Rails.application.config.api_only
     end
 
     test "api_only generator config is set when api_only is set" do
@@ -1940,6 +1940,18 @@ module ApplicationTests
       assert_equal Digest::SHA1, ActiveSupport::Digest.hash_digest_class
     end
 
+    test "custom serializers should be able to set via config.active_job.custom_serializers in an initializer" do
+      class ::DummySerializer < ActiveJob::Serializers::ObjectSerializer; end
+
+      app_file "config/initializers/custom_serializers.rb", <<-RUBY
+      Rails.application.config.active_job.custom_serializers << DummySerializer
+      RUBY
+
+      app "development"
+
+      assert_includes ActiveJob::Serializers.serializers, DummySerializer
+    end
+
     private
       def force_lazy_load_hooks
         yield # Tasty clarifying sugar, homie! We only need to reference a constant to load it.
diff --git a/railties/test/application/console_test.rb b/railties/test/application/console_test.rb
index 13164f49c2..4a14042cd3 100644
--- a/railties/test/application/console_test.rb
+++ b/railties/test/application/console_test.rb
@@ -73,7 +73,7 @@ class ConsoleTest < ActiveSupport::TestCase
     MODEL
 
     load_environment
-    assert User.new.respond_to?(:name)
+    assert_respond_to User.new, :name
 
     app_file "app/models/user.rb", <<-MODEL
       class User
@@ -81,9 +81,9 @@ class ConsoleTest < ActiveSupport::TestCase
       end
     MODEL
 
-    assert !User.new.respond_to?(:age)
+    assert_not_respond_to User.new, :age
     irb_context.reload!(false)
-    assert User.new.respond_to?(:age)
+    assert_respond_to User.new, :age
   end
 
   def test_access_to_helpers
diff --git a/railties/test/application/content_security_policy_test.rb b/railties/test/application/content_security_policy_test.rb
index 97f2957c33..0d28df16f8 100644
--- a/railties/test/application/content_security_policy_test.rb
+++ b/railties/test/application/content_security_policy_test.rb
@@ -16,7 +16,7 @@ module ApplicationTests
       teardown_app
     end
 
-    test "default content security policy is empty" do
+    test "default content security policy is nil" do
       controller :pages, <<-RUBY
         class PagesController < ApplicationController
           def index
@@ -34,7 +34,33 @@ module ApplicationTests
       app("development")
 
       get "/"
-      assert_equal ";", last_response.headers["Content-Security-Policy"]
+      assert_nil last_response.headers["Content-Security-Policy"]
+    end
+
+    test "empty content security policy is generated" do
+      controller :pages, <<-RUBY
+        class PagesController < ApplicationController
+          def index
+            render html: "<h1>Welcome to Rails!</h1>"
+          end
+        end
+      RUBY
+
+      app_file "config/initializers/content_security_policy.rb", <<-RUBY
+        Rails.application.config.content_security_policy do |p|
+        end
+      RUBY
+
+      app_file "config/routes.rb", <<-RUBY
+        Rails.application.routes.draw do
+          root to: "pages#index"
+        end
+      RUBY
+
+      app("development")
+
+      get "/"
+      assert_policy ""
     end
 
     test "global content security policy in an initializer" do
@@ -61,7 +87,7 @@ module ApplicationTests
       app("development")
 
       get "/"
-      assert_policy "default-src 'self' https:;"
+      assert_policy "default-src 'self' https:"
     end
 
     test "global report only content security policy in an initializer" do
@@ -90,7 +116,7 @@ module ApplicationTests
       app("development")
 
       get "/"
-      assert_policy "default-src 'self' https:;", report_only: true
+      assert_policy "default-src 'self' https:", report_only: true
     end
 
     test "override content security policy in a controller" do
@@ -121,7 +147,7 @@ module ApplicationTests
       app("development")
 
       get "/"
-      assert_policy "default-src https://example.com;"
+      assert_policy "default-src https://example.com"
     end
 
     test "override content security policy to report only in a controller" do
@@ -150,7 +176,7 @@ module ApplicationTests
       app("development")
 
       get "/"
-      assert_policy "default-src 'self' https:;", report_only: true
+      assert_policy "default-src 'self' https:", report_only: true
     end
 
     test "global content security policy added to rack app" do
@@ -174,7 +200,7 @@ module ApplicationTests
       app("development")
 
       get "/"
-      assert_policy "default-src 'self' https:;"
+      assert_policy "default-src 'self' https:"
     end
 
     private
diff --git a/railties/test/application/initializers/frameworks_test.rb b/railties/test/application/initializers/frameworks_test.rb
index d2b77bd015..e631318f82 100644
--- a/railties/test/application/initializers/frameworks_test.rb
+++ b/railties/test/application/initializers/frameworks_test.rb
@@ -266,7 +266,7 @@ module ApplicationTests
         ActiveRecord::Base.connection
       RUBY
       require "#{app_path}/config/environment"
-      assert !ActiveRecord::Base.connection_pool.active_connection?
+      assert_not_predicate ActiveRecord::Base.connection_pool, :active_connection?
     end
   end
 end
diff --git a/railties/test/application/loading_test.rb b/railties/test/application/loading_test.rb
index de1e240fd3..2632dd7cde 100644
--- a/railties/test/application/loading_test.rb
+++ b/railties/test/application/loading_test.rb
@@ -352,11 +352,11 @@ class LoadingTest < ActiveSupport::TestCase
   def test_initialize_can_be_called_at_any_time
     require "#{app_path}/config/application"
 
-    assert !Rails.initialized?
-    assert !Rails.application.initialized?
+    assert_not_predicate Rails, :initialized?
+    assert_not_predicate Rails.application, :initialized?
     Rails.initialize!
-    assert Rails.initialized?
-    assert Rails.application.initialized?
+    assert_predicate Rails, :initialized?
+    assert_predicate Rails.application, :initialized?
   end
 
   private
diff --git a/railties/test/application/mailer_previews_test.rb b/railties/test/application/mailer_previews_test.rb
index 4e77cece1b..ba186bda44 100644
--- a/railties/test/application/mailer_previews_test.rb
+++ b/railties/test/application/mailer_previews_test.rb
@@ -296,7 +296,7 @@ module ApplicationTests
     test "mailer preview not found" do
       app("development")
       get "/rails/mailers/notifier"
-      assert last_response.not_found?
+      assert_predicate last_response, :not_found?
       assert_match "Mailer preview &#39;notifier&#39; not found", last_response.body
     end
 
@@ -326,7 +326,7 @@ module ApplicationTests
       app("development")
 
       get "/rails/mailers/notifier/bar"
-      assert last_response.not_found?
+      assert_predicate last_response, :not_found?
       assert_match "Email &#39;bar&#39; not found in NotifierPreview", last_response.body
     end
 
@@ -382,7 +382,7 @@ module ApplicationTests
       app("development")
 
       get "/rails/mailers/notifier/foo?part=text%2Fhtml"
-      assert last_response.not_found?
+      assert_predicate last_response, :not_found?
       assert_match "Email part &#39;text/html&#39; not found in NotifierPreview#foo", last_response.body
     end
 
@@ -450,11 +450,67 @@ module ApplicationTests
 
       get "/rails/mailers/notifier/foo.html"
       assert_equal 200, last_response.status
-      assert_match '<option selected value="?part=text%2Fhtml">View as HTML email</option>', last_response.body
+      assert_match '<option selected value="part=text%2Fhtml">View as HTML email</option>', last_response.body
 
       get "/rails/mailers/notifier/foo.txt"
       assert_equal 200, last_response.status
-      assert_match '<option selected value="?part=text%2Fplain">View as plain-text email</option>', last_response.body
+      assert_match '<option selected value="part=text%2Fplain">View as plain-text email</option>', last_response.body
+    end
+
+    test "locale menu selects correct option" do
+      app_file "config/initializers/available_locales.rb", <<-RUBY
+        Rails.application.configure do
+          config.i18n.available_locales = %i[en ja]
+        end
+      RUBY
+
+      mailer "notifier", <<-RUBY
+        class Notifier < ActionMailer::Base
+          default from: "from@example.com"
+
+          def foo
+            mail to: "to@example.org"
+          end
+        end
+      RUBY
+
+      html_template "notifier/foo", <<-RUBY
+        <p>Hello, World!</p>
+      RUBY
+
+      text_template "notifier/foo", <<-RUBY
+        Hello, World!
+      RUBY
+
+      mailer_preview "notifier", <<-RUBY
+        class NotifierPreview < ActionMailer::Preview
+          def foo
+            Notifier.foo
+          end
+        end
+      RUBY
+
+      app("development")
+
+      get "/rails/mailers/notifier/foo.html"
+      assert_equal 200, last_response.status
+      assert_match '<option selected value="locale=en">en', last_response.body
+      assert_match '<option  value="locale=ja">ja', last_response.body
+
+      get "/rails/mailers/notifier/foo.html?locale=ja"
+      assert_equal 200, last_response.status
+      assert_match '<option  value="locale=en">en', last_response.body
+      assert_match '<option selected value="locale=ja">ja', last_response.body
+
+      get "/rails/mailers/notifier/foo.txt"
+      assert_equal 200, last_response.status
+      assert_match '<option selected value="locale=en">en', last_response.body
+      assert_match '<option  value="locale=ja">ja', last_response.body
+
+      get "/rails/mailers/notifier/foo.txt?locale=ja"
+      assert_equal 200, last_response.status
+      assert_match '<option  value="locale=en">en', last_response.body
+      assert_match '<option selected value="locale=ja">ja', last_response.body
     end
 
     test "mailer previews create correct links when loaded on a subdirectory" do
@@ -520,8 +576,8 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo.txt"
       assert_equal 200, last_response.status
       assert_match '<iframe seamless name="messageBody" src="?part=text%2Fplain">', last_response.body
-      assert_match '<option selected value="?part=text%2Fplain">', last_response.body
-      assert_match '<option  value="?part=text%2Fhtml">', last_response.body
+      assert_match '<option selected value="part=text%2Fplain">', last_response.body
+      assert_match '<option  value="part=text%2Fhtml">', last_response.body
 
       get "/rails/mailers/notifier/foo?part=text%2Fplain"
       assert_equal 200, last_response.status
@@ -530,8 +586,8 @@ module ApplicationTests
       get "/rails/mailers/notifier/foo.html?name=Ruby"
       assert_equal 200, last_response.status
       assert_match '<iframe seamless name="messageBody" src="?name=Ruby&amp;part=text%2Fhtml">', last_response.body
-      assert_match '<option selected value="?name=Ruby&amp;part=text%2Fhtml">', last_response.body
-      assert_match '<option  value="?name=Ruby&amp;part=text%2Fplain">', last_response.body
+      assert_match '<option selected value="name=Ruby&amp;part=text%2Fhtml">', last_response.body
+      assert_match '<option  value="name=Ruby&amp;part=text%2Fplain">', last_response.body
 
       get "/rails/mailers/notifier/foo?name=Ruby&part=text%2Fhtml"
       assert_equal 200, last_response.status
diff --git a/railties/test/application/middleware/cache_test.rb b/railties/test/application/middleware/cache_test.rb
index 9822ec563d..3768d8ce2d 100644
--- a/railties/test/application/middleware/cache_test.rb
+++ b/railties/test/application/middleware/cache_test.rb
@@ -140,7 +140,7 @@ module ApplicationTests
       etag = last_response.headers["ETag"]
 
       get "/expires/expires_etag", { private: true }, { "HTTP_IF_NONE_MATCH" => etag }
-      assert_equal     "miss", last_response.headers["X-Rack-Cache"]
+      assert_equal "miss", last_response.headers["X-Rack-Cache"]
       assert_not_equal body,   last_response.body
     end
 
@@ -174,7 +174,7 @@ module ApplicationTests
       last = last_response.headers["Last-Modified"]
 
       get "/expires/expires_last_modified", { private: true }, { "HTTP_IF_MODIFIED_SINCE" => last }
-      assert_equal     "miss", last_response.headers["X-Rack-Cache"]
+      assert_equal "miss", last_response.headers["X-Rack-Cache"]
       assert_not_equal body,   last_response.body
     end
   end
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index d59384e982..5efaf841d4 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -45,7 +45,8 @@ module ApplicationTests
         "ActionDispatch::ContentSecurityPolicy::Middleware",
         "Rack::Head",
         "Rack::ConditionalGet",
-        "Rack::ETag"
+        "Rack::ETag",
+        "Rack::TempfileReaper"
       ], middleware
     end
 
diff --git a/railties/test/application/rake/migrations_test.rb b/railties/test/application/rake/migrations_test.rb
index 788f9160d6..bf5b07afbd 100644
--- a/railties/test/application/rake/migrations_test.rb
+++ b/railties/test/application/rake/migrations_test.rb
@@ -29,12 +29,32 @@ module ApplicationTests
 
         assert_match(/AMigration: migrated/, output)
 
+        # run all the migrations to test scope for down
+        output = rails("db:migrate")
+        assert_match(/CreateUsers: migrated/, output)
+
         output = rails("db:migrate", "SCOPE=bukkits", "VERSION=0")
         assert_no_match(/drop_table\(:users\)/, output)
         assert_no_match(/CreateUsers/, output)
         assert_no_match(/remove_column\(:users, :email\)/, output)
 
         assert_match(/AMigration: reverted/, output)
+
+        output = rails("db:migrate", "VERSION=0")
+
+        assert_match(/CreateUsers: reverted/, output)
+      end
+
+      test "version outputs current version" do
+        app_file "db/migrate/01_one_migration.rb", <<-MIGRATION
+          class OneMigration < ActiveRecord::Migration::Current
+          end
+        MIGRATION
+
+        rails "db:migrate"
+
+        output = rails("db:version")
+        assert_match(/Current version: 1/, output)
       end
 
       test "migrate with specified VERSION in different formats" do
diff --git a/railties/test/application/rake_test.rb b/railties/test/application/rake_test.rb
index 5a6404bd0a..d134febaf4 100644
--- a/railties/test/application/rake_test.rb
+++ b/railties/test/application/rake_test.rb
@@ -2,7 +2,6 @@
 
 require "isolation/abstract_unit"
 require "env_helpers"
-require "active_support/core_ext/string/strip"
 
 module ApplicationTests
   class RakeTest < ActiveSupport::TestCase
@@ -131,7 +130,7 @@ module ApplicationTests
       RUBY
 
       output = rails("routes")
-      assert_equal <<-MESSAGE.strip_heredoc, output
+      assert_equal <<~MESSAGE, output
                               Prefix Verb URI Pattern                                                                       Controller#Action
                                 cart GET  /cart(.:format)                                                                   cart#show
                   rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
@@ -173,7 +172,7 @@ module ApplicationTests
       RUBY
 
       output = rails("routes", "-g", "show")
-      assert_equal <<-MESSAGE.strip_heredoc, output
+      assert_equal <<~MESSAGE, output
                               Prefix Verb URI Pattern                                                                       Controller#Action
                                 cart GET  /cart(.:format)                                                                   cart#show
                   rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
@@ -183,7 +182,7 @@ module ApplicationTests
       MESSAGE
 
       output = rails("routes", "-g", "POST")
-      assert_equal <<-MESSAGE.strip_heredoc, output
+      assert_equal <<~MESSAGE, output
                               Prefix Verb URI Pattern                                    Controller#Action
                                      POST /cart(.:format)                                cart#create
                 rails_direct_uploads POST /rails/active_storage/direct_uploads(.:format) active_storage/direct_uploads#create
@@ -242,7 +241,7 @@ module ApplicationTests
         end
       RUBY
 
-      assert_equal <<-MESSAGE.strip_heredoc, rails("routes")
+      assert_equal <<~MESSAGE, rails("routes")
                               Prefix Verb URI Pattern                                                                       Controller#Action
                   rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
                 rails_blob_variation GET  /rails/active_storage/variants/:signed_blob_id/:variation_key/*filename(.:format) active_storage/variants#show
@@ -262,7 +261,7 @@ module ApplicationTests
 
       output = Dir.chdir(app_path) { `bin/rake --rakefile Rakefile routes` }
 
-      assert_equal <<-MESSAGE.strip_heredoc, output
+      assert_equal <<~MESSAGE, output
                               Prefix Verb URI Pattern                                                                       Controller#Action
                                 cart GET  /cart(.:format)                                                                   cart#show
                   rails_service_blob GET  /rails/active_storage/blobs/:signed_id/*filename(.:format)                        active_storage/blobs#show
diff --git a/railties/test/application/runner_test.rb b/railties/test/application/runner_test.rb
index aa5d495c97..8f5f48c281 100644
--- a/railties/test/application/runner_test.rb
+++ b/railties/test/application/runner_test.rb
@@ -107,13 +107,13 @@ module ApplicationTests
 
     def test_runner_detects_syntax_errors
       output = rails("runner", "puts 'hello world", allow_failure: true)
-      assert_not $?.success?
+      assert_not_predicate $?, :success?
       assert_match "unterminated string meets end of file", output
     end
 
     def test_runner_detects_bad_script_name
       output = rails("runner", "iuiqwiourowe", allow_failure: true)
-      assert_not $?.success?
+      assert_not_predicate $?, :success?
       assert_match "undefined local variable or method `iuiqwiourowe' for", output
     end
 
diff --git a/railties/test/application/test_runner_test.rb b/railties/test/application/test_runner_test.rb
index a01325fdb8..8e5ccf94cc 100644
--- a/railties/test/application/test_runner_test.rb
+++ b/railties/test/application/test_runner_test.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "isolation/abstract_unit"
-require "active_support/core_ext/string/strip"
 require "env_helpers"
 
 module ApplicationTests
@@ -502,10 +501,10 @@ module ApplicationTests
     end
 
     def test_output_inline_by_default
-      create_test_file :models, "post", pass: false
+      create_test_file :models, "post", pass: false, print: false
 
       output = run_test_command("test/models/post_test.rb")
-      expect = %r{Running:\n\nPostTest\nF\n\nFailure:\nPostTest#test_truth \[[^\]]+test/models/post_test.rb:6\]:\nwups!\n\nbin/rails test test/models/post_test.rb:4\n\n\n\n}
+      expect = %r{Running:\n\nF\n\nFailure:\nPostTest#test_truth \[[^\]]+test/models/post_test.rb:6\]:\nwups!\n\nbin/rails test test/models/post_test.rb:4\n\n\n\n}
       assert_match expect, output
     end
 
@@ -523,6 +522,28 @@ module ApplicationTests
         capture(:stderr) { run_test_command("test/models/post_test.rb --fail-fast", stderr: true) })
     end
 
+    def test_run_in_parallel_with_processes
+      file_name = create_parallel_processes_test_file
+
+      output = run_test_command(file_name)
+
+      assert_match %r{Finished in.*\n2 runs, 2 assertions}, output
+    end
+
+    def test_run_in_parallel_with_threads
+      app_path("/test/test_helper.rb") do |file_name|
+        file = File.read(file_name)
+        file.sub!(/parallelize\(([^\)]*)\)/, "parallelize(\\1, with: :threads)")
+        File.write(file_name, file)
+      end
+
+      file_name = create_parallel_threads_test_file
+
+      output = run_test_command(file_name)
+
+      assert_match %r{Finished in.*\n2 runs, 2 assertions}, output
+    end
+
     def test_raise_error_when_specified_file_does_not_exist
       error = capture(:stderr) { run_test_command("test/not_exists.rb", stderr: true) }
       assert_match(%r{cannot load such file.+test/not_exists\.rb}, error)
@@ -718,7 +739,7 @@ module ApplicationTests
       def create_model_with_fixture
         rails "generate", "model", "user", "name:string"
 
-        app_file "test/fixtures/users.yml", <<-YAML.strip_heredoc
+        app_file "test/fixtures/users.yml", <<~YAML
           vampire:
             id: 1
             name: Koyomi Araragi
@@ -800,19 +821,70 @@ module ApplicationTests
         RUBY
       end
 
-      def create_test_file(path = :unit, name = "test", pass: true)
+      def create_test_file(path = :unit, name = "test", pass: true, print: true)
         app_file "test/#{path}/#{name}_test.rb", <<-RUBY
           require 'test_helper'
 
           class #{name.camelize}Test < ActiveSupport::TestCase
             def test_truth
-              puts "#{name.camelize}Test"
+              puts "#{name.camelize}Test" if #{print}
               assert #{pass}, 'wups!'
             end
           end
         RUBY
       end
 
+      def create_parallel_processes_test_file
+        app_file "test/models/parallel_test.rb", <<-RUBY
+          require 'test_helper'
+
+          class ParallelTest < ActiveSupport::TestCase
+            RD1, WR1 = IO.pipe
+            RD2, WR2 = IO.pipe
+
+            test "one" do
+              WR1.close
+              assert_equal "x", RD1.read(1) # blocks until two runs
+
+              RD2.close
+              WR2.write "y" # Allow two to run
+              WR2.close
+            end
+
+            test "two" do
+              RD1.close
+              WR1.write "x" # Allow one to run
+              WR1.close
+
+              WR2.close
+              assert_equal "y", RD2.read(1) # blocks until one runs
+            end
+          end
+        RUBY
+      end
+
+      def create_parallel_threads_test_file
+        app_file "test/models/parallel_test.rb", <<-RUBY
+          require 'test_helper'
+
+          class ParallelTest < ActiveSupport::TestCase
+            Q1 = Queue.new
+            Q2 = Queue.new
+            test "one" do
+              assert_equal "x", Q1.pop # blocks until two runs
+
+              Q2 << "y"
+            end
+
+            test "two" do
+              Q1 << "x"
+
+              assert_equal "y", Q2.pop # blocks until one runs
+            end
+          end
+        RUBY
+      end
+
       def create_env_test
         app_file "test/unit/env_test.rb", <<-RUBY
           require 'test_helper'
diff --git a/railties/test/application/test_test.rb b/railties/test/application/test_test.rb
index 0a51e98656..fb43bebfbe 100644
--- a/railties/test/application/test_test.rb
+++ b/railties/test/application/test_test.rb
@@ -7,10 +7,15 @@ module ApplicationTests
     include ActiveSupport::Testing::Isolation
 
     def setup
+      @old = ENV["PARALLEL_WORKERS"]
+      ENV["PARALLEL_WORKERS"] = "0"
+
       build_app
     end
 
     def teardown
+      ENV["PARALLEL_WORKERS"] = @old
+
       teardown_app
     end
 
diff --git a/railties/test/commands/console_test.rb b/railties/test/commands/console_test.rb
index 45ab8d87ff..b7cdb8229e 100644
--- a/railties/test/commands/console_test.rb
+++ b/railties/test/commands/console_test.rb
@@ -20,30 +20,30 @@ class Rails::ConsoleTest < ActiveSupport::TestCase
 
   def test_sandbox_option
     console = Rails::Console.new(app, parse_arguments(["--sandbox"]))
-    assert console.sandbox?
+    assert_predicate console, :sandbox?
   end
 
   def test_short_version_of_sandbox_option
     console = Rails::Console.new(app, parse_arguments(["-s"]))
-    assert console.sandbox?
+    assert_predicate console, :sandbox?
   end
 
   def test_no_options
     console = Rails::Console.new(app, parse_arguments([]))
-    assert !console.sandbox?
+    assert_not_predicate console, :sandbox?
   end
 
   def test_start
     start
 
-    assert app.console.started?
+    assert_predicate app.console, :started?
     assert_match(/Loading \w+ environment \(Rails/, output)
   end
 
   def test_start_with_sandbox
     start ["--sandbox"]
 
-    assert app.console.started?
+    assert_predicate app.console, :started?
     assert app.sandbox
     assert_match(/Loading \w+ environment in sandbox \(Rails/, output)
   end
diff --git a/railties/test/commands/credentials_test.rb b/railties/test/commands/credentials_test.rb
index 7c464b3fde..663ee73bcd 100644
--- a/railties/test/commands/credentials_test.rb
+++ b/railties/test/commands/credentials_test.rb
@@ -43,6 +43,18 @@ class Rails::Command::CredentialsCommandTest < ActiveSupport::TestCase
     assert_match(/api_key: abc/, run_show_command)
   end
 
+  test "edit command does not add master key when `RAILS_MASTER_KEY` env specified" do
+    Dir.chdir(app_path) do
+      key = IO.binread("config/master.key").strip
+      FileUtils.rm("config/master.key")
+
+      switch_env("RAILS_MASTER_KEY", key) do
+        run_edit_command
+        assert_not File.exist?("config/master.key")
+      end
+    end
+  end
+
   test "show credentials" do
     assert_match(/access_key_id: 123/, run_show_command)
   end
diff --git a/railties/test/commands/encrypted_test.rb b/railties/test/commands/encrypted_test.rb
index 6647dcc902..9fc73d5f18 100644
--- a/railties/test/commands/encrypted_test.rb
+++ b/railties/test/commands/encrypted_test.rb
@@ -33,6 +33,18 @@ class Rails::Command::EncryptedCommandTest < ActiveSupport::TestCase
     end
   end
 
+  test "edit command does not add master key when `RAILS_MASTER_KEY` env specified" do
+    Dir.chdir(app_path) do
+      key = IO.binread("config/master.key").strip
+      FileUtils.rm("config/master.key")
+
+      switch_env("RAILS_MASTER_KEY", key) do
+        run_edit_command("config/tokens.yml.enc")
+        assert_not File.exist?("config/master.key")
+      end
+    end
+  end
+
   test "edit encrypts file with custom key" do
     run_edit_command("config/tokens.yml.enc", key: "config/tokens.key")
 
diff --git a/railties/test/engine_test.rb b/railties/test/engine_test.rb
index 4bd8a07085..19379e200c 100644
--- a/railties/test/engine_test.rb
+++ b/railties/test/engine_test.rb
@@ -11,7 +11,7 @@ class EngineTest < ActiveSupport::TestCase
       end
     end
 
-    assert !engine.routes?
+    assert_not_predicate engine, :routes?
   end
 
   def test_application_can_be_subclassed
diff --git a/railties/test/generators/api_app_generator_test.rb b/railties/test/generators/api_app_generator_test.rb
index 4815cf6362..9c523ad372 100644
--- a/railties/test/generators/api_app_generator_test.rb
+++ b/railties/test/generators/api_app_generator_test.rb
@@ -13,7 +13,7 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
     Rails.application = TestApp::Application
     super
 
-    Kernel::silence_warnings do
+    Kernel.silence_warnings do
       Thor::Base.shell.send(:attr_accessor, :always_force)
       @shell = Thor::Base.shell.new
       @shell.send(:always_force=, true)
@@ -63,6 +63,23 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_generator_if_skip_action_mailer_is_given
+    run_generator [destination_root, "--api", "--skip-action-mailer"]
+    assert_file "config/application.rb", /#\s+require\s+["']action_mailer\/railtie["']/
+    assert_file "config/environments/development.rb" do |content|
+      assert_no_match(/config\.action_mailer/, content)
+    end
+    assert_file "config/environments/test.rb" do |content|
+      assert_no_match(/config\.action_mailer/, content)
+    end
+    assert_file "config/environments/production.rb" do |content|
+      assert_no_match(/config\.action_mailer/, content)
+    end
+    assert_no_directory "app/mailers"
+    assert_no_directory "test/mailers"
+    assert_no_directory "app/views"
+  end
+
   def test_app_update_does_not_generate_unnecessary_config_files
     run_generator
 
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index 60b9ff1317..99790e602d 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -219,6 +219,8 @@ class AppGeneratorTest < Rails::Generators::TestCase
     run_generator [app_root]
     output = nil
 
+    assert_file "#{app_root}/config/application.rb", /\s+config\.load_defaults #{Rails::VERSION::STRING.to_f}/
+
     Dir.chdir(app_root) do
       output = `./bin/rails r "puts Rails.application.config.assets.unknown_asset_fallback"`
     end
@@ -313,6 +315,15 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_file "Gemfile", /^# gem 'mini_magick'/
   end
 
+  def test_mini_magick_gem_when_skip_active_storage_is_given
+    app_root = File.join(destination_root, "myapp")
+    run_generator [app_root, "--skip-active-storage"]
+
+    assert_file "#{app_root}/Gemfile" do |content|
+      assert_no_match(/gem 'mini_magick'/, content)
+    end
+  end
+
   def test_app_update_does_not_generate_active_storage_contents_when_skip_active_storage_is_given
     app_root = File.join(destination_root, "myapp")
     run_generator [app_root, "--skip-active-storage"]
@@ -334,10 +345,6 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_no_file "#{app_root}/config/storage.yml"
-
-    assert_file "#{app_root}/Gemfile" do |content|
-      assert_no_match(/gem 'mini_magick'/, content)
-    end
   end
 
   def test_app_update_does_not_generate_active_storage_contents_when_skip_active_record_is_given
@@ -361,10 +368,19 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_no_file "#{app_root}/config/storage.yml"
+  end
 
-    assert_file "#{app_root}/Gemfile" do |content|
-      assert_no_match(/gem 'mini_magick'/, content)
+  def test_app_update_does_not_change_config_target_version
+    run_generator
+
+    FileUtils.cd(destination_root) do
+      config = "config/application.rb"
+      content = File.read(config)
+      File.write(config, content.gsub(/config\.load_defaults #{Rails::VERSION::STRING.to_f}/, "config.load_defaults 5.1"))
+      quietly { system("bin/rails app:update") }
     end
+
+    assert_file "config/application.rb", /\s+config\.load_defaults 5\.1/
   end
 
   def test_application_names_are_not_singularized
@@ -638,6 +654,13 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_empty output
   end
 
+  def test_force_option_overwrites_every_file_except_master_key
+    run_generator [File.join(destination_root, "myapp")]
+    output = run_generator [File.join(destination_root, "myapp"), "--force"]
+    assert_match(/force/, output)
+    assert_no_match("force  config/master.key", output)
+  end
+
   def test_application_name_with_spaces
     path = File.join(destination_root, "foo bar")
 
diff --git a/railties/test/generators/controller_generator_test.rb b/railties/test/generators/controller_generator_test.rb
index a3218951a6..91e4a86775 100644
--- a/railties/test/generators/controller_generator_test.rb
+++ b/railties/test/generators/controller_generator_test.rb
@@ -109,4 +109,11 @@ class ControllerGeneratorTest < Rails::Generators::TestCase
       assert_match(/^  namespace :admin do\n    get 'dashboard\/index'\n    get 'dashboard\/show'\n  end$/, route)
     end
   end
+
+  def test_does_not_add_routes_when_action_is_not_specified
+    run_generator ["admin/dashboard"]
+    assert_file "config/routes.rb" do |routes|
+      assert_no_match(/namespace :admin/, routes)
+    end
+  end
 end
diff --git a/railties/test/generators/create_migration_test.rb b/railties/test/generators/create_migration_test.rb
index 3cb7fd6baa..2ae38045c5 100644
--- a/railties/test/generators/create_migration_test.rb
+++ b/railties/test/generators/create_migration_test.rb
@@ -70,7 +70,7 @@ class CreateMigrationTest < Rails::Generators::TestCase
     create_migration
 
     assert_match(/identical  db\/migrate\/1_create_articles\.rb\n/, invoke!)
-    assert @migration.identical?
+    assert_predicate @migration, :identical?
   end
 
   def test_invoke_when_exists_not_identical
diff --git a/railties/test/generators/generated_attribute_test.rb b/railties/test/generators/generated_attribute_test.rb
index c6f7bdeda1..772b4f6f0d 100644
--- a/railties/test/generators/generated_attribute_test.rb
+++ b/railties/test/generators/generated_attribute_test.rb
@@ -104,25 +104,25 @@ class GeneratedAttributeTest < Rails::Generators::TestCase
 
   def test_reference_is_true
     %w(references belongs_to).each do |attribute_type|
-      assert create_generated_attribute(attribute_type).reference?
+      assert_predicate create_generated_attribute(attribute_type), :reference?
     end
   end
 
   def test_reference_is_false
     %w(foo bar baz).each do |attribute_type|
-      assert !create_generated_attribute(attribute_type).reference?
+      assert_not_predicate create_generated_attribute(attribute_type), :reference?
     end
   end
 
   def test_polymorphic_reference_is_true
     %w(references belongs_to).each do |attribute_type|
-      assert create_generated_attribute("#{attribute_type}{polymorphic}").polymorphic?
+      assert_predicate create_generated_attribute("#{attribute_type}{polymorphic}"), :polymorphic?
     end
   end
 
   def test_polymorphic_reference_is_false
     %w(foo bar baz).each do |attribute_type|
-      assert !create_generated_attribute("#{attribute_type}{polymorphic}").polymorphic?
+      assert_not_predicate create_generated_attribute("#{attribute_type}{polymorphic}"), :polymorphic?
     end
   end
 
@@ -148,7 +148,7 @@ class GeneratedAttributeTest < Rails::Generators::TestCase
     att = Rails::Generators::GeneratedAttribute.parse("supplier:references{required}:index")
     assert_equal "supplier", att.name
     assert_equal :references, att.type
-    assert att.has_index?
-    assert att.required?
+    assert_predicate att, :has_index?
+    assert_predicate att, :required?
   end
 end
diff --git a/railties/test/generators/model_generator_test.rb b/railties/test/generators/model_generator_test.rb
index 516aa0704f..8d933e82c3 100644
--- a/railties/test/generators/model_generator_test.rb
+++ b/railties/test/generators/model_generator_test.rb
@@ -2,7 +2,6 @@
 
 require "generators/generators_test_helper"
 require "rails/generators/rails/model/model_generator"
-require "active_support/core_ext/string/strip"
 
 class ModelGeneratorTest < Rails::Generators::TestCase
   include GeneratorsTestHelper
@@ -379,10 +378,10 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_required_belongs_to_adds_required_association
     run_generator ["account", "supplier:references{required}"]
 
-    expected_file = <<-FILE.strip_heredoc
-    class Account < ApplicationRecord
-      belongs_to :supplier, required: true
-    end
+    expected_file = <<~FILE
+      class Account < ApplicationRecord
+        belongs_to :supplier, required: true
+      end
     FILE
     assert_file "app/models/account.rb", expected_file
   end
@@ -390,10 +389,10 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_required_polymorphic_belongs_to_generages_correct_model
     run_generator ["account", "supplier:references{required,polymorphic}"]
 
-    expected_file = <<-FILE.strip_heredoc
-    class Account < ApplicationRecord
-      belongs_to :supplier, polymorphic: true, required: true
-    end
+    expected_file = <<~FILE
+      class Account < ApplicationRecord
+        belongs_to :supplier, polymorphic: true, required: true
+      end
     FILE
     assert_file "app/models/account.rb", expected_file
   end
@@ -401,10 +400,10 @@ class ModelGeneratorTest < Rails::Generators::TestCase
   def test_required_and_polymorphic_are_order_independent
     run_generator ["account", "supplier:references{polymorphic.required}"]
 
-    expected_file = <<-FILE.strip_heredoc
-    class Account < ApplicationRecord
-      belongs_to :supplier, polymorphic: true, required: true
-    end
+    expected_file = <<~FILE
+      class Account < ApplicationRecord
+        belongs_to :supplier, polymorphic: true, required: true
+      end
     FILE
     assert_file "app/models/account.rb", expected_file
   end
@@ -452,11 +451,11 @@ class ModelGeneratorTest < Rails::Generators::TestCase
 
   def test_token_option_adds_has_secure_token
     run_generator ["user", "token:token", "auth_token:token"]
-    expected_file = <<-FILE.strip_heredoc
-    class User < ApplicationRecord
-      has_secure_token
-      has_secure_token :auth_token
-    end
+    expected_file = <<~FILE
+      class User < ApplicationRecord
+        has_secure_token
+        has_secure_token :auth_token
+      end
     FILE
     assert_file "app/models/user.rb", expected_file
   end
diff --git a/railties/test/generators/plugin_generator_test.rb b/railties/test/generators/plugin_generator_test.rb
index fc7584c175..28ac3611b7 100644
--- a/railties/test/generators/plugin_generator_test.rb
+++ b/railties/test/generators/plugin_generator_test.rb
@@ -82,11 +82,12 @@ class PluginGeneratorTest < Rails::Generators::TestCase
   end
 
   def test_generating_in_full_mode_with_almost_of_all_skip_options
-    run_generator [destination_root, "--full", "-M", "-O", "-C", "-S", "-T"]
+    run_generator [destination_root, "--full", "-M", "-O", "-C", "-S", "-T", "--skip-active-storage"]
     assert_file "bin/rails" do |content|
       assert_no_match(/\s+require\s+["']rails\/all["']/, content)
     end
     assert_file "bin/rails", /#\s+require\s+["']active_record\/railtie["']/
+    assert_file "bin/rails", /#\s+require\s+["']active_storage\/engine["']/
     assert_file "bin/rails", /#\s+require\s+["']action_mailer\/railtie["']/
     assert_file "bin/rails", /#\s+require\s+["']action_cable\/engine["']/
     assert_file "bin/rails", /#\s+require\s+["']sprockets\/railtie["']/
@@ -216,12 +217,22 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_javascripts_generation
     run_generator [destination_root, "--mountable"]
-    assert_file "app/assets/javascripts/bukkits/application.js"
+    assert_file "app/assets/javascripts/bukkits/application.js" do |content|
+      assert_match "//= require rails-ujs", content
+      assert_match "//= require activestorage", content
+      assert_match "//= require_tree .", content
+    end
+    assert_file "app/views/layouts/bukkits/application.html.erb" do |content|
+      assert_match "javascript_include_tag", content
+    end
   end
 
   def test_skip_javascripts
     run_generator [destination_root, "--skip-javascript", "--mountable"]
     assert_no_file "app/assets/javascripts/bukkits/application.js"
+    assert_file "app/views/layouts/bukkits/application.html.erb" do |content|
+      assert_no_match "javascript_include_tag", content
+    end
   end
 
   def test_template_from_dir_pwd
@@ -320,8 +331,11 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "app/helpers/bukkits/application_helper.rb", /module Bukkits\n  module ApplicationHelper/
     assert_file "app/views/layouts/bukkits/application.html.erb" do |contents|
       assert_match "<title>Bukkits</title>", contents
+      assert_match "<%= csrf_meta_tags %>", contents
+      assert_match "<%= csp_meta_tag %>", contents
       assert_match(/stylesheet_link_tag\s+['"]bukkits\/application['"]/, contents)
       assert_match(/javascript_include_tag\s+['"]bukkits\/application['"]/, contents)
+      assert_match "<%= yield %>", contents
     end
     assert_file "test/test_helper.rb" do |content|
       assert_match(/ActiveRecord::Migrator\.migrations_paths.+\.\.\/test\/dummy\/db\/migrate/, content)
diff --git a/railties/test/generators/shared_generator_tests.rb b/railties/test/generators/shared_generator_tests.rb
index 97d43af60a..aa577e4234 100644
--- a/railties/test/generators/shared_generator_tests.rb
+++ b/railties/test/generators/shared_generator_tests.rb
@@ -9,7 +9,7 @@ module SharedGeneratorTests
     super
     Rails::Generators::AppGenerator.instance_variable_set("@desc", nil)
 
-    Kernel::silence_warnings do
+    Kernel.silence_warnings do
       Thor::Base.shell.send(:attr_accessor, :always_force)
       @shell = Thor::Base.shell.new
       @shell.send(:always_force=, true)
diff --git a/railties/test/generators_test.rb b/railties/test/generators_test.rb
index 1735804664..9f1f2a2289 100644
--- a/railties/test/generators_test.rb
+++ b/railties/test/generators_test.rb
@@ -64,7 +64,7 @@ class GeneratorsTest < Rails::Generators::TestCase
     assert File.exist?(File.join(@path, "generators", "model_generator.rb"))
     assert_called_with(Rails::Generators::ModelGenerator, :start, [["Account"], {}]) do
       warnings = capture(:stderr) { Rails::Generators.invoke :model, ["Account"] }
-      assert warnings.empty?
+      assert_empty warnings
     end
   end
 
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 6568a356d6..0a4d2a9167 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -38,7 +38,12 @@ module TestHelpers
     end
 
     def app_path(*args)
-      tmp_path(*%w[app] + args)
+      path = tmp_path(*%w[app] + args)
+      if block_given?
+        yield path
+      else
+        path
+      end
     end
 
     def framework_path
diff --git a/railties/test/minitest/rails_plugin_test.rb b/railties/test/minitest/rails_plugin_test.rb
new file mode 100644
index 0000000000..7c3a2022a9
--- /dev/null
+++ b/railties/test/minitest/rails_plugin_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class Minitest::RailsPluginTest < ActiveSupport::TestCase
+  setup do
+    @options = Minitest.process_args []
+    @output = StringIO.new("".encode("UTF-8"))
+  end
+
+  test "default reporters are replaced" do
+    with_reporter Minitest::CompositeReporter.new do |reporter|
+      reporter << Minitest::SummaryReporter.new(@output, @options)
+      reporter << Minitest::ProgressReporter.new(@output, @options)
+      reporter << Minitest::Reporter.new(@output, @options)
+
+      Minitest.plugin_rails_init({})
+
+      assert_equal 3, reporter.reporters.count
+      assert reporter.reporters.any? { |candidate| candidate.kind_of?(Minitest::SuppressedSummaryReporter) }
+      assert reporter.reporters.any? { |candidate| candidate.kind_of?(::Rails::TestUnitReporter) }
+      assert reporter.reporters.any? { |candidate| candidate.kind_of?(Minitest::Reporter) }
+    end
+  end
+
+  test "no custom reporters are added if nothing to replace" do
+    with_reporter Minitest::CompositeReporter.new do |reporter|
+      Minitest.plugin_rails_init({})
+
+      assert_empty reporter.reporters
+    end
+  end
+
+  private
+    def with_reporter(reporter)
+      old_reporter, Minitest.reporter = Minitest.reporter, reporter
+
+      yield reporter
+    ensure
+      Minitest.reporter = old_reporter
+    end
+end
diff --git a/railties/test/paths_test.rb b/railties/test/paths_test.rb
index 854b4448a4..9f5bb37c20 100644
--- a/railties/test/paths_test.rb
+++ b/railties/test/paths_test.rb
@@ -104,7 +104,7 @@ class PathsTest < ActiveSupport::TestCase
     File.stub(:exist?, true) do
       @root.add "app", with: "/app"
       @root["app"].autoload_once!
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.autoload_once, @root["app"].expanded.first
     end
   end
@@ -112,17 +112,17 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to remove a path that should be autoloaded only once" do
     @root["app"] = "/app"
     @root["app"].autoload_once!
-    assert @root["app"].autoload_once?
+    assert_predicate @root["app"], :autoload_once?
 
     @root["app"].skip_autoload_once!
-    assert !@root["app"].autoload_once?
+    assert_not_predicate @root["app"], :autoload_once?
     assert_not_includes @root.autoload_once, @root["app"].expanded.first
   end
 
   test "it is possible to add a path without assignment and specify it should be loaded only once" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", autoload_once: true
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.autoload_once, "/app"
     end
   end
@@ -130,7 +130,7 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to add multiple paths without assignment and specify it should be loaded only once" do
     File.stub(:exist?, true) do
       @root.add "app", with: ["/app", "/app2"], autoload_once: true
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.autoload_once, "/app"
       assert_includes @root.autoload_once, "/app2"
     end
@@ -158,7 +158,7 @@ class PathsTest < ActiveSupport::TestCase
     File.stub(:exist?, true) do
       @root["app"] = "/app"
       @root["app"].eager_load!
-      assert @root["app"].eager_load?
+      assert_predicate @root["app"], :eager_load?
       assert_includes @root.eager_load, @root["app"].to_a.first
     end
   end
@@ -166,17 +166,17 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to skip a path from eager loading" do
     @root["app"] = "/app"
     @root["app"].eager_load!
-    assert @root["app"].eager_load?
+    assert_predicate @root["app"], :eager_load?
 
     @root["app"].skip_eager_load!
-    assert !@root["app"].eager_load?
+    assert_not_predicate @root["app"], :eager_load?
     assert_not_includes @root.eager_load, @root["app"].to_a.first
   end
 
   test "it is possible to add a path without assignment and mark it as eager" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", eager_load: true
-      assert @root["app"].eager_load?
+      assert_predicate @root["app"], :eager_load?
       assert_includes @root.eager_load, "/app"
     end
   end
@@ -184,7 +184,7 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to add multiple paths without assignment and mark them as eager" do
     File.stub(:exist?, true) do
       @root.add "app", with: ["/app", "/app2"], eager_load: true
-      assert @root["app"].eager_load?
+      assert_predicate @root["app"], :eager_load?
       assert_includes @root.eager_load, "/app"
       assert_includes @root.eager_load, "/app2"
     end
@@ -193,8 +193,8 @@ class PathsTest < ActiveSupport::TestCase
   test "it is possible to create a path without assignment and mark it both as eager and load once" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", eager_load: true, autoload_once: true
-      assert @root["app"].eager_load?
-      assert @root["app"].autoload_once?
+      assert_predicate @root["app"], :eager_load?
+      assert_predicate @root["app"], :autoload_once?
       assert_includes @root.eager_load, "/app"
       assert_includes @root.autoload_once, "/app"
     end
@@ -254,7 +254,7 @@ class PathsTest < ActiveSupport::TestCase
   test "a path can be added to the load path on creation" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", load_path: true
-      assert @root["app"].load_path?
+      assert_predicate @root["app"], :load_path?
       assert_equal ["/app"], @root.load_paths
     end
   end
@@ -271,7 +271,7 @@ class PathsTest < ActiveSupport::TestCase
   test "a path can be marked as autoload on creation" do
     File.stub(:exist?, true) do
       @root.add "app", with: "/app", autoload: true
-      assert @root["app"].autoload?
+      assert_predicate @root["app"], :autoload?
       assert_equal ["/app"], @root.autoload_paths
     end
   end
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index 339a56c34f..a59c63f343 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -34,7 +34,7 @@ module RailtiesTest
 
     def migrations
       migration_root = File.expand_path(ActiveRecord::Migrator.migrations_paths.first, app_path)
-      ActiveRecord::Migrator.migrations(migration_root)
+      ActiveRecord::MigrationContext.new(migration_root).migrations
     end
 
     test "serving sprocket's assets" do
diff --git a/version.rb b/version.rb
index 2cc861a1bd..54bfbdd516 100644
--- a/version.rb
+++ b/version.rb
@@ -7,10 +7,10 @@ module Rails
   end
 
   module VERSION
-    MAJOR = 5
-    MINOR = 2
+    MAJOR = 6
+    MINOR = 0
     TINY  = 0
-    PRE   = "beta2"
+    PRE   = "alpha"
 
     STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
   end